I just did this a few weeks ago on my '04. The process really was quite simple. On both sides of the radio are trim pieces that extend from the top of the radio down to the bottom of the storage bin (they don't go around the top or bottom. just trying to give you reference point). All you need to do is pry these 2 pieces off. I started at the bottom. I used a screw driver to get underneath the trim piece but that was probably a bad choice of tools since I scratched the grey plastic on the adjoining dash piece slightly (probably only noticeable by me). Once you get these 2 trim pieces off the hard work is done. Next it's a matter of removing the 4 screws holding the radio/storage bin assembly in. These screws should be obvious to you. Now the radio/storage bin assembly can be removed. Unplug the wiring harness and antenna. Now remove the screws that fasten the radio to the storage bin. It really only took me about 5 minutes to get the old radio out. For the installation I used a wiring harness which cost me $10. You should definitely get one. As far as mounting the new radio, I re-used the storage bin/radio assembly. All I had to do was enlarge a couple of the holes in the factory mounting assembly because the new radio mounting screws were of larger diameter. You'll also notice that on top of the storage bin there are a couple of nubs that fit into the factory stereo. I had to remove these. I used a wood chisel. You could probably use a utility knife or figure something else out. Just be careful to stay away from the front edge so you don't mar any plastic that will show. It was definitely worth saving the $20 that a new mounting kit would cost. And I can only imagine that the only difference would be it doesn't have the nubs and maybe more and/or larger mounting holes. If it ever warms up above the single digits here I can take some pictures of how to remove the trim and give you an idea of what to expect when you open it up. This was the first time I ever mounted a stereo and was not nearly as bad as I thought it would be. One last note. You will need to use the trim piece that goes around the face on the new radio.
Good luck and let me know if you still have questions.

Update 5/19/2005: Finally, pictures.
http://pic6.picturetrail.com/VOL144/1003147/7441242/97250467.jpg
http://pic6.picturetrail.com/VOL144/1003147/7441242/97250460.jpg
http://pic6.picturetrail.com/VOL144/1003147/7441242/97250457.jpg
http://pic6.picturetrail.com/VOL144/1003147/7441242/97250454.jpg
http://pic6.picturetrail.com/VOL144/1003147/7441242/97250450.jpg

Removing the stock stereo is pretty easy... once you get the covers off. There are two plastic panels, one on each side of the stereo. These pieces come off. I used a credit card to remove them, sliding the card behind the pointy end and edging it carefully upward until the bottom became unsnapped. Then I just pulled on the wider part of the panel and the whole thing popped off. Easy.

Then you will see that the stereo is held in by two screws, one on each side. Use a long screw driver to get these (might want to use one with a magnetic head so the damn screws don't fall off into your dash, although they will probably just fall out onto the floor).

The harness has a clip on it. Just push down on the clip and pop it off. The antennae is plugged in with a very old school banana connector. Easy. Just yank it out.

Then you are done. There is not much play with the wires. The manufacturer did not waste any money on excess wiring and you will find it hard to select a good remote connection if you are installing an amp. I eventually just tapped into the cigarette lighter. But even that connection had NO slack. Every wire is either coated in foam or has plastic loom around it or both! So good luck. I would certainly recommend a wiring harness adapter if you can get one with whatever head you buy. Get it from crutchfield. They will likely have it and will include it for free.

The pannels snap back into place easily and tightly. You could remove the other four screws for the other dash units (incuding the ac controls) if you need more room to maneuver or are installing a double din head.