Wow ! Talk about thread revival.
I'm still using this rig, although I have upgraded the electronics goodies.
Anyway, to answer your question:
The case was easily disassembled by drilling out the rivets with a 1/8" drill bit. I just picked a vertical height that I thought would look great, then cut all of the vertical pieces off by the same amount. I was pretty careful about my cut-off decision though, because I still wanted to utilize as much of the plastic face as possible. There were specific design features of the plastic that pointed me to a particular height. Had I started with a completely different case I might have made it a different height. I only needed a minimum height for my radiator, so I picked a convenient height that was more than the min but would look cosmetically appealing.
By far, the longest part of this process was painting all of the metal. Cutting the plastic was done with a cut-off wheel (Dremel) followed by filing. I just drew some straight lines with a square and followed the lines, then sanded/filed until I was satisfied.
The metal frame parts were cut with the same Dremel tool. Side panels were cut using a jig saw with a metal cutting blade (cheap!). Rivets were replaced using a hand rivet gun from Home Depot and Aluminum rivets. Make sure to do all of your cutting before you paint of course! Also, if you don't plan to paint, I recommend covering everything (and I mean EVERYTHING) with tape so that nothing is scratched with your tools.