HENDERSON, MINN. -- Allie Weber, a 55-year-old corn farmer, pulled his cane-backed chair up to the parish house table for eggs and sausage and gestured to Sister JoAnne Backes, seated on his left. Backes, a Benedictine nun, presides over brunch at St. Joseph Roman Catholic Church -- and over the church.

"Why shouldn't she be ordained?" Weber asked.

Parishioners here and at St. Thomas in nearby Jessenland have no resident priest. Backes, 45, is everything but. She leads communion prayer services twice a week. She helps celebrate mass with a priest who serves four parishes and comes once a week. She instructs couples in the sacrament of marriage and comforts relatives of the dying.

More important, she has persuaded the farmers, small retailers and homemakers who make up her two parishes to play ecclesiastical roles they would not have contemplated before she arrived four years ago. They now read the Bible at mass, design parts of the service for their children, manage the parish budget and debate getting rid of the old wooden communion rail that stands between Backes and them.

In addition to doing things differently, they have begun to think differently. They remain respectful of church teaching, but they have come to see it more as guidance, and they are making up their own THE PAPAL VISIT Second of Three Articles minds about such formerly unambiguous issues as divorce and remarriage, married priests and birth control.

The reception given to Backes, and her impact here, are remarkable in a community where cherry phosphates at the corner drugstore still cost a dime. But these traditional Roman Catholics, of German and Irish descent, are also pragmatists, and they accepted Backes because they knew that priests were in short supply. Almost unanimously, they say they feel renewed energy to work for the church to which she has introduced them.

"It's like -- what is it those Baptists call it -- being born again," said Michael Skelly, 65, whose farm has been in his family for more than a century.

In many ways, the 150 families of these two parishes are living Vatican II, the worldwide council of bishops convened by Pope John XXIII in the early 1960s to foster aggiornamento, a revitalization of the church. The pope said he wanted to open the windows and let in fresh air.

The council challenged churches to make worship more accessible to the faithful, redefining the church as the whole people of God. Masses began to be celebrated in the vernacular; priests faced their congregations for the first time, and the laity acquired new responsibility. Such rapid change left some Americans confused about what it means to be Catholic.

Internal change was accompanied by enormous demographic shifts. Until about 1950, Catholics were largely blue-collar European immigrants living unto themselves in working-class urban neighborhoods. In 1947, they made up about 20 percent of the U.S. population, according to pollster George Gallup Jr.

Then Catholic men began attending college on the GI Bill, and Catholic families began moving to the suburbs. The percentage of Americans calling themselves Catholic has risen to 28 percent, according to Gallup, and they are middle class by most measures.

As a group, they are wealthier than most Protestants, except Episcopalians and Presbyterians, and almost half have some college instruction. They are young -- about 30 percent are under 30 -- and they marry non-Catholics almost half the time.

Fifty-three percent of them go to mass weekly, a figure that has stabilized after a decade of decline, and 44 percent are actively involved in their church, a higher proportion than in any other western nation.

The new laity has had a tremendous impact on church institutions, not all of it positive from the Vatican's point of view. The Rev. Charles Curran, teaching theology at the Catholic University of America, designed his instruction in sexual ethics to speak to contemporary Catholics and was censured by the Vatican. He was suspended from the faculty by university chancellor and Washington Archbishop James A. Hickey. Seattle Archbishop Raymond G. Hunthausen relaxed disciplinary procedures for homosexuals and divorced Catholics and was stripped temporarily of several powers.

But overall, lay leadership has revitalized the American church, according to the National Conference of Catholic Bishops, which has designed the upcoming papal visit in the hopes that John Paul II will see this phenomenon and approve of it. "Lay people want encouragement from the pope, not scolding," said Dolores Leckey, who directs the bishops' laity office.Pioneering in the West

Partly because there are fewer priests west of the Mississippi than in the East, western Catholics have tended to pioneer new roles for the laity. Yet even here, parishes in neighboring communities have accommodated to change at very different rates.

In Henderson, where the population has been 728 for a decade, the combined forces of Backes and necessity have prompted parishioners to embrace and promote change in an unlikely place. In the booming Minneapolis suburbs of Eden Prairie and Bloomington, the young members of Pax Christi Catholic Community are assuming leadership in the church as they are assuming similar roles in their civic and business lives. In downtown St. Paul, St. Agnes Roman Catholic Church has moved cautiously to involve its members in running the parish while preserving tradition.

Harold Hughesdon, 66, has been attending St. Agnes since he arrived from England 40 years ago. For him, this 100-year-old baroque structure, with its copper-covered onion dome, is a gem in a once-thriving Austrian neighborhood that now consists largely of deteriorating homes, boarded-up businesses and adult bookstores.

As the population of St. Paul has declined -- from 313,000 in 1960 to 270,000 in 1980 -- parish registration has dropped from about 1,500 families to about 1,250 families. St. Agnes' pastor, Msgr. Richard Schuler, has attempted to stop the decline by offering disappearing forms of worship, including a Latin mass accompanied by a 60-member chorale.

"I'm antediluvian," he says, adding that he has adopted "the reforms the church has asked me to."

Last year, Schuler made Hughesdon one of two permanent deacons, a new position for the parish that allows Hughesdon to do such things as minister to the sick and perform administrative duties. A director of technology for Minnesota Mining & Manufacturing Co., Hughesdon enjoys being a leader in his church as well.

But he contends that many American Catholics -- lay members and clergy -- have taken their new responsibility too far. He is particularly critical of Catholics who press for the ordination of women and married men.

"The church is a club," he said over Sunday afternoon tea in his comfortable, two-story white frame house about a half-mile from the church. "If you want, you can leave." The pope's position that Catholic teaching is nonnegotiable sits well in the Hughesdon household, particularly now that the five children have left home.

Two sons, who no longer attend church, and three daughters, who do, have not always agreed with or obeyed the church's teachings on premarital sex, marriage and birth control, Hughesdon and his wife, Dolores, said, choosing their words in that careful way parents have of talking about beloved, independent children.

"There are so many options these days to help break the commandments," Dolores Hughesdon said with a sigh. "It's a very difficult time to be Catholic."

The Hughesdons say St. Agnes' weekly rituals are what help them to "be Catholic."

Entering one of the parish's six Sunday services is like stepping back in time. Schuler, in robe and shawl, faces the altar, his back to the congregation. He is assisted primarily by another priest. Older worshipers chant parts of the service from memory. Some women wear lace veils over their hair; men and women finger rosary beads. They take communion kneeling at the altar, not standing in the post-Vatican II manner.

The most obvious symbol of the old is the sanctuary. While some Catholic churches have removed filigree and ornate statues, believing that they impede dialogue with God, Schuler is spending more than $1 million to repaint the St. Agnes ceiling in rose, scallop it in white and gold and erect a metallic "sunburst" over the altar. 'Community' in the Suburbs

By contrast, the Pax Christi Catholic Community is a vision of the future, a sweeping, modern shingled structure on a winding subdivision road named Pioneer Trail.

Formed six years ago at the request of 200 families in the Minneapolis suburbs of Eden Prairie and Bloomington, it now serves 2,200 families. Almost 200 infants were baptized at Pax Christi last year; only 14 members died.

Larry and Mary Erickson attended their first service there in late 1981, having just returned from Disneyland with their five children. The Rev. Timothy Power, appointed to Pax Christi on the laity's recommendation, was preaching that the church should not be an amusement park for forgetting life stresses, but a place where people are challenged to confront their problems. "It was as if he were preaching to us," Mary Erickson recalled.

Erickson, 39, sits on the church's community council, three laymen and three laywomen who set priorities for church programs and spending.

Erickson, in high school during Vatican II and now studying for a master's degree in theology, says several of the church's moral teachings are not compatible with her idea of Christian justice: Divorced Catholics should not be excluded from the sacraments, she says; birth control should be permitted, "except for the IUD {intrauterine device} which destroys a fetus." Even abortion, in some cases, might be acceptable: "The spirit is leading me to believe that aborting a fetus could be the sacrifice of one human being for the sake of another."

"Living within the church, I have learned to be sensitive both to its teachings and to my conscience," she says. "There are things I love dearly about the church and things for which I feel mortal embarrassment. But I continue to hold that tension. My willingness to do that, and others' willingness, will be the ultimate salvation of the church."

Erickson says she is supported in her beliefs by other members of the Pax Christi "community," a slogan adopted by some churches after Vatican II to indicate mutual acceptance among equals. The word is at the heart of the three Sunday worship services at Pax Christi.

The church interior resembles an orchestra hall, with the congregation facing the worship leaders on three sides. Bible readings, congregational responses and hymns are flashed onto two huge video screens. The congregation sings and claps, accompanied by a guitarist. At communion, participants stand to receive wine and wafers from a pastor and 11 lay assistants.

Fr. Power, sometimes wearing a buttoned-down shirt and khaki slacks, works the crowd after church. "How ya doing?" he asks. "How's your mother? Gonna play golf today?"

Two full-time lay administrators help Power manage the parish, and two lay pastoral ministers counsel the sick and troubled. Power has resisted the idea -- suggested by higher church authorities -- of bringing in another full-time clergyman. An Inclusive 'Vision Keeper'

He sees his job as "vision keeper" and includes everyone in that vision, including homosexuals and remarried adults. The church has become known in the area as "the Care-Bear parish" after the cuddly stuffed animal, several members say.

Even the language of its 50-plus ministries is designed to convey approval. The old church, according to Power, would have asked a couple preparing for marriage whether they were registered Catholics and attended mass. "Our question would be 'Why are you here?' " he said, "and 'How do you and God get along?' "

While many Pax Christi members embrace the idea that the church should offer options, not absolutes, some are beginning to question the long-term implications. "What do I tell my children is part of the Catholic tradition worth holding on to?" asks Mary Lou Carney, 34. "I hear from members that we no longer challenge people. They say, 'I can use birth control, I can get divorced and remarried, I can, I can, I can.'

"Maybe it's not enough just to work at feeling good. Maybe we need a little guilt to challenge us."

Forty miles southwest of Pax Christi, Marge Smith and her friends at St. Joseph's and St. Thomas' are asking some of these same questions. The tone of their questions is less perplexed, perhaps because they have not discarded so much of their past.

Marge and Harold Smith moved to Henderson 13 years ago from a congregation similar to Pax Christi's, and they were surprised at what they found. St. Joseph's, its white steeple towering over the valley, was an idyllic spot for worship, but few people took part. Revitalization Through Participation

Congregational life was resurrected, Marge Smith says, as Sister Jo gradually introduced participatory forms of worship. Last Easter-time, members reenacted a scene from the New Testament in which Jesus washes the feet of his disciples. "Twelve people were up there {in the church} having their feet washed," Smith recalls with a smile. "I never thought I'd see that here."

Smith, naturally shy, also never thought she would lead a communion service, but she does whenever Backes is out of town.

Smith recalls that when Bishop Raymond Lucker sent Backes to their parish as a "pastoral administrator," one of about 30 in the country, her husband asked, "What can she do for us?" Backes was an oddity, the first thing the town had had to talk about since the night in 1980 when Ed the Pig, an 810-pound native hog, wallowed his way onto "The Tonight Show" with Johnny Carson.

But Harold Smith and others soon decided that the diminutive nun with the infectious laugh was a big improvement over a succession of aging, ill or part-time priests. She not only draws them into the rituals of the church but reminds them of the profound spirituality in life's ordinary rituals. Henderson Independent editor Leonard Blaschko says Backes attends almost every wedding party given in the American Legion Hall, often blessing the food and dancing with the celebrants.

Backes peppers her homily and prayers with references to the commonplace. During one Tuesday morning communion service, she talked about how difficult it is to trust in God, "for we need to know there's a check coming at the end of the month." She then prayed for the pope's upcoming visit, "for the Traxler family as they prepare for their new baby, and for Chris Chadwick and John Vraa who are getting married this Saturday."

Later, around Backes' oak table, Marge Henrich, 74, reported she saw a pheasant in her back yard. Marge Smith complained that "Wagar's Market ran out of milk on Monday." Someone mentioned the pope's upcoming visit.

"I'd like to see him," said Smith, and several others nodded. "But I wouldn't go very far to do it."