Insulation
There are kinds of insulation "foam" which does not conduct much heat. I believe some can be found at your local hardware store, people sell similar things in packages, but they're much more expensive. I'm not exactly sure what its called, just look around, you should find it.
As for cooling, fans should still be optimal, especially if your not good with the inside of your computer. Be warned, watercooling is a great way to keep your components cool, but the risks are equally high.