Fridge all of a sudden started getting incredibly cold, fridge portion is at high 20's and freezer is -20. Compressor seems to be running non stop! In the past we had our cold control knob at almost the warmest setting, I made sure it had not been touched... even moving it to the off position does not turn it off! Think it's the thermostat, no idea where to find a replacement part and install instructions, can anyone help?

The hard part is going to be finding out the model... a sticker with some instructions on the top of the fridge door says Part No 934111 which I don't think is the model number. There is a metal plate on the bottom of the fridge when you open the door, problem is this there is rust and the lettering as to what's the serial/model/etc is rubbed off, so here are the numbers imprinted on the plate:
8630583 (think this is the model number)
E50810766
Type 19ATR85

This is an OLD fridge (I don't know what year, it was given to us free), is it worth repairing or should we just go buy a new one? Thanks for your help!