I believe the right question would be, what lens should you buy, but not what camera. A d5000 with do fine but for a wedding, I would (and that's just me) go with a 85mm for portraits and a 18-105 or a nice16-85 to capture whatever the party is going to throw at you. Oh and get a speedlight, like a sb600 so you can shoot at a decent iso on the dance floor. CHeers!