Nice setup and oc there 2a. It's good to see ppl trying ideas like this. I used to do something similar but with a 12 can cooler full of ice water. Of course I had everything insulated so no worries about condensation. The socket area on your mobo looks very easy to insulate.
Instead of using ice chunks, try freezing some bottles of water and adding/removing them as temps rise. It would be a much less aggressive cooling so you should be able to avoid condensation while still maintaining excellent temps. If you're going to game several hours then start with more liquid volume. One of those plastic storage bins would work great for this. They're only like $10, 22-30gal capacity and have a sealed top. A large beer cooler would be best as they're insulated but can be expensive. Silent sub-ambient cooling..nice!
If that's a compressor works trans cooler then it has aluminium tubes. http://www.compressorworks.com/default.aspx?page=TransOilCoolers
You'll need a corrosion inhibitor.. I recommend using 10% Zerex Racing Super Coolant. Of course that is only to be used in a sealed loop for safety reasons.
A heater core probably would have been a better choice. One of the best cores to use is for a 77' Olds 98.. those are around $30-$35 at Autozone.