I've replaced the factory stereo on every vehicle I've owned and the Liberty is no exception. I ordered a JVC stereo, Pioneer speakers, and Sirius adapter from Crutchfield. I ordered 4-way speakers for the front doors and 2-ways for the rear doors. The installation was a simple remove and replace using the included adapters. I mounted the Sirius adapter under the center console storage pocket.
One modification I did do was to power the radio with a 'delayed off' wire. This way the radio will stay on for several minutes or until a door is opened. I tapped this wire off the power wire for the windows (pink w/yellow stripe).
Another modification I did was get rid of the dorky factory antenna. I bought one of those amplified European style swept back antennas and mounted it in front of the rear overhead brake light.
The factory antenna unscrews to the point where it will fall inside the fender. The best way I found to remove it is to loosen the fender bolts and pull the fender back enough to reach inside and remove the factory antenna. I covered the hole with a "Trail Rated" badge I got on Ebay.