Passages. Transition. Prime time marches on.

This year on network television - that other world where Americans spend great chunks of their lives - Richie, Potsie, Ralph Malph and even Fonzie have graduated on "Happy Days." Later this month, Fonzie will actually be baptized.

On Saturday night, Mary Lou, Murray and others will be fired from their seven-year-old jobs on "The Mary Tyler Moore Show" as the series comes to its first-run end.

And tonight, another milestone: Maj. Margaret (Hot Lips) Houlihan will be married to Lt. Col. Donald Penobscott on "M*A*S*H," the long-running CBS comedy hit at 9 p.m. on Channel 9.

Like the thus-jilted Maj. Burns, with whom Houlihan has for several seasons indulged in poorly disguised hanky-panky, we will adjust but, at first, it may be hard for people to get used. They will have several weeks of reruns, starting next week, to help them through the period of adjustment.

It's quite a wedding. Klinger, in an Alice Blue Gown with matching hat, starts crying right away.

The Hot Lips nuptials may not mark a new high for "M*A*S*H," but the installment, las t new one of the season, serves to remind us again of what has made the show run longer than the Korean War in which it is set. It is beautifully acted, well-written, and includes characters recognizably human and durable enough to survive the obligatory gags that decorate the scripts.

Essentially, these characters comprise a family, one doing its best to cope with circumstances over which it has pitifully little control. They are basically symbolic of all families. "M*A*S*H" is not a war comedy nor even an antiwar comedy. It is a weekly statement on behalf of survival and strong, amusing case for tolerance of one's fellow poor suckers.

Tonight's episode was written by Everett Greenbaum and Jim Fritzell and directed by Gene Reynolds. Though Loretta Swit as Hot Lips totters off in a helicopter near the close, Swit is scheduled to return next season, as are Alan Alda, Harry Morgan, Larry Linville, Gary Burghoff, and others. Plus ca change, as the Frenchmen say, but in this case, hip-hip and hooray for thememe chose.