A Good Guy Who Wears Two Hats

He played an intense, moody Secret Service agent in 1985's To Live and Die in L.A., and an intense, moody FBI agent in 1986's Manhunter(opposite Brian Cox's Hannibal ''the Cannibal'' Lecter in Lecter's first, pre-Silence of the Lambs movie appearance). Now William Petersen, 39, is taking on a different role: He's playing an intense, moody artist-turned-cowboy in Keep the Change. ''(Thomas) McGuane's characters are always a little quirky,'' says Petersen. ''But they're so rich, so expressive. There isn't an actor around who wouldn't kill to play one of them.'' Petersen didn't have to kill to get the part — he just had to produce the film, something he has been doing a lot of lately. Earlier this year he produced Hard Promises, a theatrical release in which he costarred with Sissy Spacek. Appearing opposite Petersen in Change are Buck Henry as his boozy uncle (who wants to become Montana's first shrimp wrangler) and recent Oscar winner Jack Palance as his arch-enemy (''He's in great shape,'' says Petersen. ''The one-arm push-up didn't surprise me a bit''). Next on Petersen's to-do list: a play opening this summer called Once in Doubt, produced by Petersen's own Chicago theater company. ''It's very disturbing and comical,'' he says. Intense and moody, too.