It's located behind the brake booster. Right hand side of the engine bay when looking from the front of the car, back against the firewall.
http://www.grandprixforums.net/2000-...ube-65867.html
Take a look at post #7 from that link, by BillBoost, that's how I plan on doing mine. Just be careful with the lines.
I'm assuming that you're replacing that, the evap, and possibly the compressor? Get an A/C o-ring kit and replace every seal you run into along the way to save yourself the headache. And after it's all together, get it charged properly, as in pull a vacuum on the system, and if it holds, charge with the correct amount of freeon and oil.
