I did that upgrade last winter. It's a simple plug and play. Only I hard thing to do.
The installation instructions that come along are pretty explanatory.
http://site.justforjeeps.com/guide/82208269.pdf
Need to run the wire harness on the right side of the jeep, unscrew the 4 bolts holding your unit in place and plug the new harness in.
CAUTION! Disconnecting the radio unit from it's power source, will reset the unit and you will NEDD A RADIO CODE to reactivate it! If you don't have the radio code for your unit, you ca get it from any dealer (requires your VIN and proof of ownership).
The right hand quarter panel is held on by clips you need to force them out. Start from the cargo area and move towards the rear seat.
You will also need to remove the rear right seatbelt so that you can take the entire quarter panel out of the jeep.
This is what you will be looking at when you take out the panel.
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The reason you want it out is (here comes the hard part) that you have to cut a rectangular piece, the size of the changer, out of the quarter panel.
A template is included to help you out.
Don't get scared, it sounds worst than it really is.
A Cd-changer surrounding trim is supplied to cover up any mistakes and give you a factory look.
The material it self is not that hard to cut. I did it with a sharp blade.
Here is a detailed write-up.(bowdown)
http://www.jeepprojects.com/content.php?article.13.0
Hope this helps