question about the TCC

I just had a used transmission put in my car, and when i was driving around 45-50 and then slowed to a stop, the car stalled out completely. Started up fine, stayed running in R and N, but when put it drive, stalls. Eventually, i got it to move, and took it to my mechanic. I assumed it had to deal with the TCC solenoid, after reading many threads with the same symptoms. So my mechanic un-plugged it, and it fixed it. Do i need to replace the TCC solenoid? or the Torque Converter itself? If the solenoid, how much would that run? and is it difficult? thanks.

You just need to replace the TCC solenoid itself.
Leaving the TCC unplug would cause you minor negative fuel mileage efficiency. The TCC is used and locked up at the highest tranny gear when you are at cruising speed and you get good fuel economy.