I did this modification as well; It's been very worthwhile. Kenwood DNX-8120 makes an excellent factory-look in-dash NAV system. iPod interface is excellent as well.
I had absolutely zero experience installing / working on car stereo equipment, and I managed to pull this off in a few nights. Most of my time was spent reading the instructions and comparing to what I saw in the car, so I bet I could get this done in an afternoon if I had to do it again.
I couldn't recommend this upgrade to you enough. Do it! Treat yourself.
***edit*** If you are any good with electronics, the blue LEDs started to get to me on the Kenwood after a while... I may pull the car apart again while she's sleeping the winter away and see if I can swap the blues for some dimmer amber LEDs...