I agree with the above post except for the bit about the license plate lights. I've converted my dome/map/license plate lights to LEDs with no problems. The only thing you need to worry about is the fact that the license plate bulbs actually run at just over 14v, not 12v. This means that they will quickly destroy any 12v LEDs you put back there. My suggestion, as you will find elsewhere, is to use a set from 42draftdesigns. They make the license plate bulbs that can handle the voltage.
I bought a set from SuperBrightLEDs.com and they lasted about 4 weeks. The set I bought from 42draftdesigns is going on 6 months with no problems at all.
There is also a thread somewhere that goes over the install. If you can find it, I added a bunch of pictures and a semi-walkthrough.