I have a 1999 TL and it has basically the same interior. I wouldn't bother using a stock GPS for 2 reasons.
1. the A/C controls are in the GPS on a stock Acura
2. Taking apart your top dash you risk it being shakey and crappy when you put it back.
My TL interior
Here's what I did.
1. Took a touch screen.
2. Took a bezel for a car stereo (as if I was taking out the stock and putting in a pioneer deck)
3. Took the touch screen out of its casing and used a dremel to cut the bezel and sketched the outline of the screen directly in the center.
4. Cut the screen shape out of the bezel.
5. Glued the screen to the bezel.
6. Cleaned it up with Bondo
7 painted it flat black
The second link has more information then mine...
Here's another guys who did a better job then me
Yes you can run a radio and carputer. All you do is plug the carputer into the Aux input so you can have 3 options (CD, RADIO, Aux aka carputer) I think this is the best option because if your computer gets buggy and you need to take it out you still have a cd player. This happened to me for a good month! It's also nice because sometimes I'll take the plug out the back of the carputer and plug it into my iphone and listen to internet radio if I feel like it.
I used an M10000 motherboard and got a case for it with a startup commander that the computer plugs into.
I am going to take better pictures and make a little tutorial tomorrow.