91 Skylark 2.5 Ate my son's inheritance

I'm new to this forum and I need help. I just had the torque converter switch replaced and now reverse gear is burned out. Mechanic says "Oh, you know, new parts on old, no guarantees." Can anybody help? I'd like to continue to restore the car but a new tranny could be a deal killer right now. Is losing reverse a likely possibility when replacing the TC Solenoid?