She's got mail . . . but it'll have to be forwarded to a new address. Meg Ryan and Dennis Quaid just found a buyer for their Fifth Avenue apartment. The blonde cutie and her oh-so-slightly-dangerous ex-husband got $6.75 million for the twelfth-floor pad near the corner of 94th Street, down slightly from the asking price of $7.2 million. The spacious three-bedroom, all three bedrooms of which face Central Park, has six oversize rooms (reconfigured from eight) and cost the couple $3.1 million in 1997. Meg has reportedly been shopping downtown for new digs, but no sales have been confirmed, according to her Sotheby's broker, Anne Curran. No word on whether her upper-Fifth Avenue neighbors are sad to be losing their celebrity girl-next-door or relieved at losing the scruffy canoodling companions (Quaid, Russell Crowe) that she seems to favor.