i actually just did the same thing, although i went to a local hitch shop because i wanted the wiring done for a brakelight/turnsignal.
anyway, you want to make sure to get a class 3 hitch which should be good for 500 tougne weight and towing 5,000. the main thing about the class 3 is that it's a 2" hitch, which makes it compatible with all the quality bike carriers.
anyway, regarding the rack, i picked up a thule t2 916xtr. there are a lot of different ones to choose from. i checked out the linup from an off brand, yamikia, and thule, and for a platform rack, the t2 is the one to go with. on and off in a breeze, it adjusts to allow gate access, and nothing touches the bike frame.
