Britney has been stealing the VMA headlines with her ballyhooed comeback, but the big story is MTV’s overhaul of its signature awards show on Sunday, now in its 24th year. Last year’s ratings dropped 50 percent from 2002’s record numbers causing MTV, which needs a tuneup anyway, to brainstorm. “Our plan was to put a stick of dynamite in it, light the fuse, and blow it up,” MTV president Christina Norman told Entertainment Weekly. First, the show is moving to Las Vegas, playing the hip Palms. Cut from three to two hours, the VMAs will be shown one time and one time only (9-11 p.m., live). Gone is the traditional audience setup; now performances and awards presentations — Justin Timberlake and Beyonce dominate the trimmed-down list of eight categories — will take place throughout the hotel. Timbaland serves as the show’s maestro and oversees most of the music. “Your…TV speakers may blow,” Tim says.