U.S. Catholic bishops have taken on a staff member, the Rev. Robert Lynch of Miami, to handle details of the visit of Pope John Paul II to this country even though no one this side of the Vatican knows precisely when the pontiff is comming or where he will visit.

The major focus of his trip is expected to be the opening session of the United Nations in late September. An invitation to address the General Assembly was extended to the pope by Secretary General Kurt Waldheim last May.

Church officials expect that the pope also will make a tour of the country. Cities most frequently mentioned are Washington, Chicago, Philadelphia, Los Angeles and San Francisco.

Pope Paul VI addressed the United Nations in 1965, but made only a quick tour of New York City before returning to Rome.

Human rights activists in Korean churches said that President Carter's visit there last month was more helpful than they had expected, but quickly added that they hadn't expected much.

"In terms of my expectation, I can say I am pleased," said the Rev. Kim Kwan Suk, who heads the Korean National Council of Churches. Then he added: "From the beginning we did not expect too much. Our expectation were mostly negative."

Kim and Roman Catholic Cardinal Kim Su Hwan of Seoul, met privately with Carter. They were the only vocal critics of the government of Park Chung Hee, in whom Carter met privately during his visit there.

The church leaders were gratified by Carter's public expressions of concern over human rights in Korea. That action, according to the churchmen, will militate against a worsening of the situation there.

"Before Carter's visit, we were already anticipating a crackdown when he and the foreign press left," said the Protestant leader. "But now we have some assurance that the repression which followed (President) Ford's visit (in 1974) will not happen this time."

No sex outside marriage is the rule for seminary students in the Lutheran Church in America. The policy statement of the church's Division for Professional Leadership was issued in response to the request of seminary presidents and deans for a standard of conduct for their charges. Said the panel: "Put plainly, until persons enter the (marriage) convenant of faithfulness, they are to remain celibate."

The campaign for $1 billion to spread the Gospel worldwide, launched nearly two years ago by evangelist Bill Bright, has passed the $100 million mark, according to Here's Life International . . . Before leaving for his current trip to this country, Rhodesian Prime Minister Abel T. Muzorewa promised that all foreign missionaries expelled from that country in recent years "whose presence might be required in the country" can return . . . The American Jewish Committee and the Association of Jewish Book Publishers are planning an exhibit of books of Jewish interest at the Second International Moscow Book Fair in September.

The Very Rev. John L. M. Filippelli, pastor of St. Pius V Church in Baltimore, has been elected superior general of the Society of St. Joseph, succeeding the Very Rev. Matthew J. O'Rourke. The Rev. John H. Ricard, pastor of Holy Comforter St. Cyprian Church here has been elected consultor general of the Josephite order, which was founded more than 100 years ago to serve the needs of the black community in this country.

When the Rev. James P. Lyke, 40, is consecrated as auxiliary bishop of Cleveland next month, he will be the fifth black bishop in the Roman Catholic Church in this country and the youngest member of the hierarchy. Lyke, a Chicago native, is president of the national Black Catholic Clergy Caucus.

The Very Rev. John Vaughn has been elected minister general of the Franciscan order, the 16th successor to St. Francis of Assisi and the first American to be elected head of the worldwide order.

The Rev. William G. Black has been elected bishop-coadjutor of the Episcopal Diocese of Southern Ohio, to succeed the Rt. Rev. John M. Krumm when he retires in 1981. In Connecticut, the Rev. Arthur E. Walmsley, a leader in social action programs of the Episcopal Church and currently rector of St. Paul's Church in New Haven, has been elected bishop-coadjutor of the diocese of Connecticut.

The Rev. James A. Devereux is leaving the English department of the University of North Carolina to become rector of the Jesuit community at Georgetown University. He also will teach English literature there.

The Rev. Robert A. Harris Jr. has become pastor of the Arlington Presbyterian Church.

Rear Adm. Ross H. Trower, 57, a minister of the Lutheran Church in America, is the new chief of chaplains and director of religious ministries for the Navy.

Sister Joanna Valoni has been named chancellor of the Roman Catholic Diocese of Lafayette, the only woman and the only person who is not a priest to hold such a post in this country.

The Rev. James Moore has become pastor of the Hillandale Baptist Church.