People are always saying "television will never be the same" after this or after that. Well, television will be exactly the same after "Fernwood Night" leaves the air; it's the universe that will be altered.

Norman Lear's talk-show satire, a nightly send-up of sham showbiz sentimentality, has given us 13 weeks of amusement. It goes out tonight in a hilarious blaze of self-pity when the final show airs at 8 o'clock on Channel 20.

Host "Barth Gimble" (Martin Mull) has sold the set - including that faithful rendering of the Fernwood Rendering Plant - to cover an old payola fine from his Miami days, when he was also charged with assaulting a 13-year-old cheerleader. To meet the expenses of fighting that charge. Gimble throws a telethon that stars a crank partiot and a woman who tap dances to "I Am Woman." It nets him 400 Blue Chip Stamps.

A Lear spokesman said from Hollywood yesterday that "Fernwood 2Night" has closed down production for now, but could return as segments of Lear's "Forever Fernwood," the sequal to "Mary Hartman, Mary Hartman" which premieres Monday night on Channel 20.

Something of this bright little morsel of right-headed insanity should be preserved - especially, perhaps, Fred Willard's immaculately unctuous cohost "Jerry Hubbard." Willard was paid the ultimate compliment recently when a guest on the "Tonight" show turned to Ed McMahon and asked. "Haven't I seen you on 'Fernwood 2Night?'"

Hail Fred, Hail Fernwood, and Farewell.