other then you did some work on it now, there are many parts yards to purchase used assembly's at a much more reasonable price. Unless you have a good machine shop that makes drive shafts new, still more reasonable then what the dealer price is. Best option is tell him you want to send it back and get your money. You will find out in a quick hurry if this dealer is repudable and more willing to work with you. As all was used or not get it writing to provide both parties with there expectaions, he gets yours with the check.