LOS ANGELES - Michael Jackson is still playing to sellout crowds. Advance screenings to the music documentary Michael Jackson: This Is It sold out within two hours early Sunday as fans who began lining up three days earlier snapped up all 3,000 tickets to the Los Angeles shows. The documentary opens nationwide Oct. 28, but fans will get a sneak peek the night before in screenings at the new Regal Cinemas Stadium 14. For the theater's grand opening, the cinema will show This Is It on