They were just kids, still wet behind the ears and untested in the battleground that is show biz. But like a seasoned squad of Broadway regulars, they took over the mezzanine of the National Theatre last night to present a preview of "Shine It On," a musical revue celebrating the 40th anniversary of the USO.

The troupe of seven Catholic University students hoofed and sang its way though excerpts from the 90-minute show in preparation for an upcoming six-week tour of U.S. military bases in England and West Germany. The revue featured everthing from Benny Goodman and Frank Sinatra tunes to '50s rock and a selection from "Saturday Night Fever."

There were tap-dancing numbers, sport skits and brief monologues that comprised a capsul history of USO shows past and present.

"We've been sending our students out every year since 1952, in Korea," said Father Gilbert V. Hartke of Catholic University. "Its wonderful for my kids and the young soldiers," he said. "The peer group impact is very great since they all get together and talk after the shows."

During the tour, the troupe will stay on the bases, eating at the canteens and mixing with the enlisted people. "It's gonna be a blast, giving the soldiers a sense of happiness and home," said Mitch Landrieu, a member of the ensemble (and son of Moon Landrieu, secretary of HUD). "Some might think that this is glamorous, but it's not," noted Darryl Jones, who cowrote, directed, and performed in the show. "We're going to very remote places. People aren't aware of how cold and threatening the atmosphere can be in that situation, and we're going to try and pick up everyone's spirits."

"It's been a lot of work. We've been rehearsing since September." Jones said. Thrilled at the thought of an upcoming White House send-off by President Carter and the prospect of the adventure ahead, he admitted that everyone's efforts were "worth it"