I think just make sure you have insurance, take all the old DOT numbers off it, and display 'private vehicle' or 'Not for Hire' (not that it means much), and run. Check up on a 30 day temp tag from your state, buut I'd be tempted to skip that, insure it, and go.
Are you buying from dealer or private? If at dealer? They will put a temp tag in window, you will need to get insurance, if private? You will probably need to contact the DMV