[BR3W CITY]

If you want an in dash gps it changes things a bit, because of the size restrictions. Most in dash units for GPS/nav are double-din, so they would need a pretty big hole in the dash. You'd have to cut a pretty decent portion of dash out, and I just don't think it would be worth it.
You could consider a flip-out nav unit; it would impede with use of the ash tray while open, but thats probably negligible for most folks.

If you want to add a regular single din unit, you can do so by enlarging the radio hole to allow the unit to be slid into place. I had to modify the little bracket that comes with the radio, but just a tiny bit in order to secure it.