It should work. There will be no need to know much electrical engineering.
So without much in depth thinking and designing here is how I'd set it up (and I am no expert at all here so keep that in mind )
1) Cooler to cool the water
2) Small 90gph pump to push water through
3) Radiator of your choice
3) Zoo Med HygroTherm Humidity & Temperature Controller to set the temperature
4) two fans (from newegg or somewhere else) and 12V adjustable power supply (get one from radioshack that can supply 500mA or more current)
5) A set of hoses that fits the pump and radiator.
Now, the power supply for the pump is plugged in into the ZooMed controler and since I dunno how many presets that controller has, or whether there is a timer built in (I'm assuming there is no presents and no timer) the controller is plugged in into the timer that will activate it at night. Controller senses the temps higher than the limit and turns on water pump that supplies cold water to radiator until the temperature is 55F.
If there are presets and a timer (best case scenario) built in into the controller you will need to set the temp to 80F during the day 55F during night, and no need for additional timer. If there isn't one, and temperatures rise higher than 80F during the day, well that needs thinking.
The fans are always on to move air around in terrarium to prevent mold and air stagnation. The cooler has its own temperature regulator..
That's it. The only electrical part is connecting the fans to the power supply, but that's easy, just run two wires from it and connect the fans one after another in parallel so that they get the same voltage (there are threads here on how to do it).
That is how I plan on doing my setup.
Um what did I miss?