If you refund the money, do you have any way to verify the tranny he returns was yours? Serial Numbers? I mean, he could do the swap and send you his bad tranny back. If you decide to refund, I would tell him, he has to pay return shipping, upon receipt and verification that he sent your parts, you will refund the purchase price only. I wouldn't pay any shipping thats the buyers problem. You should probably have stated up front "As is, where is".