Totaled Transmission Help

Hey guys. So pretty much after experiencing months of jerking from a stop and bad noises my 90k mile TT premium plus 2010 needs a new transmission. I just got the car (rip) for 9k but it’s only worth 6k. My mechanic quoted a used 75k mile transmission as 8 thousand with install included, and 10k+ for a brand new transmission. The rest of the car is in good shape and has been inspected. If I were to sell the car I would honestly only get about $5k and probably have to buy a whole new car that breaks. But if I got a used transmission, it could potentially carry the car for another 100k miles or so. What would you do?