If you decide to disassemble the freezer I strongly recommend against using a reciprocating saw. They are not exactly precision instruments and its quite likely that the shell of the freezer is being used as the condenser. You will want to carefully remove all the sheet metals and then pick the foam off the copper coils you find. When your done you will likely have 2 loops of copper, the condenser and the evaporator(hot side / cold side). you could arrange so the condenser is close to the compressor and fan cool it, then submerge your evaporator coil into your coolant and your done.
Also something to keep in mind is that these freezers are designed for short duty cycles and not continuous operation like an AC unit is. Therefor its probably a much smaller compressor, it will be capable of getting your sub zero temps but in no way is it going to allow extended operation. I would say assume a long cool down with only a few hours of operation before your back above freezing followed by another long cool down.
