The old head unit comes out with two bolts. My new Alpine head unit required an oversized adaptor to fit in the large space, an antenna adapter, and beauty trim ring. I always use a wiring harness connector so I can easily put the stock stereo back in the car.
Mad Electronics has some great prices on wiring and antenna adapters. About $2 or less for each. The shipping charge is a flat $7 but this is still cheaper than buying these two products at Circuit City for $28.
I hooked up some Monster Cable brand RCA wires and ran them under the carpet on the driver side. Mad Electronics also has some nicely priced, gold plated cables. Finally, I installed my Alpine with the two factory bolts.
In the passenger floorboard, there is a rubber grommet that passes through the firewall. You will need to remove the molding to get to it. It is located behind the far right corner of the glove box. I ran my 8 gauge power wires for my amps by making the hole a little wider. In the engine compartment the wires protrude from just below the gray PCM box. This box can be removed by opening the tabs on each side and wiggling the box out. Run the power wires down the passenger side (opposite side from RCA cables). This will lessen the chance of interference.
This is the enclosure I got from Q-logic. I bought it through www.autosupermart.com for $190. According to Q-logic they match all colors of interior. That is true if your interior is either tan or gray. I had to hit mine with some vinyl color. Still, my efforts were in vain because this piece of taint lint doesn't fit. The hole for the trunk latch is centered, but my 2000 latch is slightly off-center. I might have been able to cut it to fit, but the whole cover did not sit flush with the interior. It looked like crap, the whole thing was too large, and there is no method to secure it in place. I tossed the decorative cover in a closet and kept the speaker enclosure. I recommend just getting a box enclosure. If you are using deep woofers with large magnets, you may want a custom box built that goes deeper into the well.
In the rear seat area, I took out the round speakers and replaced them with 6x9 inch 3-way JL Audio speakers.
It takes some effort to pull out the sail panels back there. Just yank out the coat hooks if the centers will not pull loose. I made a small stencil out of cardboard shaped like a 6x9 oval and used it to re-work the 6 inch speaker hole. Just get in there with a saw or some tin snips and make the hole an oval. I aligned the 6x9 at an angle so as much speaker as possible was right behind the grille. Since the magnets are deeper on most 6x9 speakers, I stuffed a piece of cardboard in the hole before installing the speaker. This keeps the magnets from losing their effect into the sheet metal of the body. Some self-tapping sheet metal screws will hold the new speakers in place.
My Alpine completely blasted the Hell out of the stock speakers in the front door. So....
I bought a set of Infinity Kappa 6.5 inch speakers with crossovers from etronics.com. They have excellent prices on stereo equipment. The prices were so good; I bought some new Infinity Kappa 6x9 speakers for the rear seat area.
DO NOT TRY TO REMOVE THE FRONT GRILLES!!!
GM just tricked us, they don't really come off without breaking. Instead, loosen up the armrest bolts (3) and the screws (2) that hold the locks, handle, and windows controls in place. Don't take this assembly apart. Now, you should be able to lift up on the lower half of the door panel and pull it out far enough to get to the front speakers. It is not necessary to remove the door panel entirely. You will need a 7mm and 1/4 inch socket to get the speaker assembly out of the door. The rest is a snap.