[Lucky]

This shouldn't be a problem. Get his loan #, bank, and payoff amount and cut two checks -- one to the bank (for the payoff amount) and the balance to the seller. You definitely don't want to give the seller the entire amount and take it on faith that he'll pay the bank. And there is no reason for him to balk at you paying the bank directly unless he is trying to pull a fast one on you. Good luck.