Watergate Judge John Sirica, whooping it up for his 78th birthday at Mel Krupin's on Friday. (Correct gift, Ear believes: A triphammer) . . . Barbara Walters, the toast of Acapulco on her first vacation in years. (Everybody's been splashing and sparkling down there, darlings. Even adorably sulky superlawyer Roy Cohn's been spotted smiling in the sunshine, in the wake of his birthday blast at Studio 54.) . . . Bill Brock's picture, finally getting framed for the wall at the Republican National Committee's headquarters. (Bill's the only former RNC chair whose pic's been missing, among all 48. Old-time middle-of-the-road Republicans were beginning to shout about Orwellian Memory Holes. You know how they carry on.) . . . Leslie Sewell, who's just celebrated her Saw Anniversary as National Public Radio D.C. bureau chieftain, has skipped to NBC. There she'll write wise words for Roger Mudd. What fun . . . Michael Ballentine, man about the Washington-Richmond Social Axis, sequestered in the Hamptons toiling on a tell-all book . . . Roger Stone, who ran the Reagan campaign in the Big Ap, hotly denying rumors that he's running for Hamilton Fish's congressional seat . . . Novelist Warren Adler, fretting. The local Homicide Division consultant on his strictly fictional book "American Quartet" is getting the beady eye from cop pals--for some of Warren's racier inventions. Literature can be a great nuisance. In the real world. Wednesday: Kazoo!