The Washington Opera, like some other cultural outfits around town, is trying to pull itself out of hock with a big gala. This one is Jan. 23 at the Kennedy Center's Terrace Theater, and for your $250 you get a rousing show, "The Washington Opera Follies of 1983," with Imogene Coca, Douglas Fairbanks Jr., Jose Ferrer, Tammy Grimes, Jerome Hines, Ethel Merman, Carol Neblett, Mstislav Rostropovich, Jean Stapleton and others. Also a cocktail party beforehand and a preview showing of the St. Laurent Rive Gauche spring collection. Later you get a champagne supper-dance at the Watergate Hotel, and a tax deduction. General director Martin Feinstein said he hopes the event will raise $100,000 of the opera's $4.1 million budget. "We raise only 40 percent of our costs from the box office and earned expenses," he said, "so we need the other 60 percent from fund-raising: beating the bushes from corporations, individuals, foundations, opera balls and the rest." After the opera lost out on a proposed $1 million congressional appropriation for 1983, Feinstein said he believes "it was generally agreed members of Congress and senators would introduce legislation next year so that groups like us and the National Symphony would be funded on an annual basis." But that's up to the arts moguls on The Hill, and remains to be seen.