Letterman’s Making List of Changes : Television: The deposed late-night king plans no drastic overhaul of the show, but has been listening to criticisms while watching his ratings plunge nearly 25% this year.

The last time David Letterman brought his CBS “Late Show” to Los Angeles, in May, 1994, he had toppled NBC’s “Tonight Show” and was being praised by critics and fans alike as the new King of Late Night.

When he begins a week of shows in Los Angeles Monday, however, it will be as a deposed monarch. His ratings have plummeted nearly 25% this year and Jay Leno’s “Tonight Show” has beaten him for 12 of the past 15 weeks.

While many industry analysts attribute Letterman’s losses largely to the disastrous turnaround in the fortunes of CBS--which has gone from first to third place in prime time and to much weaker stations in many markets around the country--some fans and critics have been complaining that the show itself has lost some of its verve.

Letterman has been listening.

“After people keep telling you the show needs changing, you’ve got to start thinking about making some changes,” he said in an interview this week. “It’s possible that, doing the show night after night, some things can get stale. We don’t plan some major overhaul; we think we’re doing a good show now, and any change alters the dynamic. We’re not going to do comedy sketches, for example--I’ve never felt comfortable putting on a costume. But we are going to make some changes that are consistent with what we try to be: a talk show with comedy.”

Letterman acknowledged that he is unhappy with what has happened at CBS since he came there from NBC in 1993.

“It’s very discouraging--I’ve never been in a situation like this. I hope that the new owners of CBS can turn it around,” he said, referring to the fact that the network is due to be sold soon to Westinghouse Electric Corp. “We just try to do the best show we can and not think about [the network problems] that we can’t change.”

He has no plans to give up the show any time soon. His initial three-year contract with CBS (paying him an estimated $14 million per year) ends next summer but the network has the option to renew it.

“If they exercise their options, I’m here till the year 2000,” Letterman said. “I could walk away tomorrow” and forfeit the salary, he added, “but the pay’s pretty good, and this is still fun.”

Come 2000, however, it will likely be a different story.

“I’ve been doing a talk show since 1980, and I’ll be 53 when my CBS contract expires,” Letterman said. “I’m here for five more years. But after that, I think it will be time to do something else with my life. I’ve thought since I was at NBC that this was not something I want to be doing forever.”

Among the changes in the works for “Late Show” are a new set and new opening graphics, beginning in January. Chris Elliott, a regular on Letterman’s NBC show, recently was signed to be a featured guest on “Late Show,” with his exact role to be determined in coming weeks.

Rob Burnett, Letterman’s longtime head writer, has returned to the show after a stint earlier this year producing “The Bonnie Hunt Show” for Letterman’s production company.

“It’s great to have him back, and we’re putting our writing staff back together,” Letterman said. He cited a recent music video by bandleader Paul Shaffer about a neighborhood deli meat-cutter (“Meat-Cuttin’ Man”) as a comedy bit that pleased him.

For its week from Los Angeles, “Late Show’s” guests will include Danny DeVito, Bruce Willis, Bonnie Raitt, Jerry Seinfeld and Arsenio Hall in his first TV appearance since his own late-night talk show ended. There also will be surprise cameos by celebrities on location around Los Angeles.

Letterman himself has been to Los Angeles more recently than in May, 1994. Last March he hosted the Academy Awards on ABC--an outing that drew good ratings but mixed reviews, with some critics saying his comedy style was not in keeping with the traditional celebration of the movie-making business in Hollywood. This week, the Academy of Motion Picture Arts and Sciences announced that Whoopi Goldberg has agreed to host next year’s telecast.

“I am disappointed,” Letterman said. “I would have liked to have had another opportunity to do it.”

Some sources have said that Letterman, who is notoriously self-critical, recently has been screening and critiquing each night’s show after it is taped. But co-executive producer Robert Morton said: “Dave has always done that. . . . We are discouraged about what’s happening at CBS, and we’ve asked for their help in promoting the show outside the network. But Dave’s a good underdog, and he knows we can’t let this get to us.”

The promotion is considered crucial. With fewer people watching CBS on any given night, letting viewers know who Letterman’s guests are each night is more difficult. CBS recently began taking ads for the show on Comedy Central and VH1, and is putting up billboards in some markets. And, to reach Letterman’s core audience of young men, once easily reached before Fox raided CBS for NFL football, the network has even taken some ads in newspaper sports sections.

“When we got here, it was like going to Disneyland,” Letterman said. “Things are different now.”