Trans Repair an installation

I restored a 1970 BMW. This shop disassembled the transmission and reassembled it. I asked them to replace seals, fluids and let me know if there were issues. They I paid them to install the transmission as we had issues connecting it to the engine. I was charged about $1500 for the work. We got the engine working a few months ago and took it for a ride. The transmission leaks and the car will not go to second gear. I talked to Bud about it and he refused to work on it or refund money for the work. He blamed it on me and my car for some reason. I paid him what he asked. He told me to sue him if I wanted to get the money back. Worst car repair transaction I have ever experienced.