Consistent with yesterday's reports that Howard K. Stern would be suing Blonde Ambition author Rita Cosby for defamation of character, the crusader for tabloid justice was served yesterday with a hefty lawsuit moments before she made her grand entrance at the book launch party being thrown in her honor. Asking if the stack of legal papers is a "love letter from [Stern attorney] Lin Wood," Cosby puts on a brave face for The Insider's cameras, insisting she stands by her allegations that Stern was a Larry-diddling prescription Pez-dispenser somewhere in the realm of an astounding 110 - 120 percent.