Unhappy buyer .What to do ???

I have to agree with everyone else. The most oustanding line in your thread is, the fact of how many passes you had made on it already and by stating appearance only visually it looked ok.. So no one can fault you for mis-representing this part as new and unused.. Let this person go out and price a whole new centersection in comparison to the "used one" you sold him. Besides if your going to buy used parts always be prepared to find, fix, or replace pieces and parts until you get it as good as new for yourself..