FWIW, I scored a 'broken' stand up freezer on Craiglist. It was broken in that the defrost timer was stuck. The compressor, coils, etc. were all fine. I just ripped out the whole timer/thermostat assembly entirely and replaced it with Auber's 2342 PID in on/off mode.
I guess my point is, find out what's specifically wrong with the fridge. It might still be perfect for your needs if you're going with a separate temp controller for fermentation.