Diddy is promising the “party of the century” to celebrate his 40th birthday on Thursday. Sean Combs will take over the Plaza Ho tel’s Grand Ballroom. He’s hired event planner Bronson Van Wyck to create a “fantasy dreamland” with fashion installations, a labyrinth, performance art and a display by “wizard of light” Bentley Meeker, who promises the lighting will grow “dimmer and sexier,” punctuated by a “blizzard of light.” Those expected include Queen Latifah, Russell Simmons, Spike Lee, Zac Posen, Lil’ Kim and a “very special” musical guest.