Question

My 2003 Pontiac Grand Am automatic transmission needed a transmission fluid and filter change.   The shop took pan off bottom of engine, put in new fluid and filters and resealed it. When I got it home, it leaked transmission fluid on the garage floor, so I took it back and they resealed it and it still leaked. I drove it about 6 weeks while out of town, but keep putting transmission fluid in it. When I came back into town, the shop owner took it to Mr. Transmission to see what was wrong. He said that the clutches had been burned and the transmission had to be rebuilt. It seems to me that this problem was caused by the shop owner not sealing it correctly to begin with; would you agree? He wants to blame it on my occasionally towing it behind my RV. Either way, is it worth replacing or should I just trade it in on a new car? .