I used the instructions on eurosportvr.com to modify my factory radio for an auxiliary audio input and it worked great! When I plug in the ipod it overrides the radio, unplug the ipod and the radio comes back on. A trip to radio shack and home depot and about 2 hours of patience with a soldering iron. I highly recommend this for anyone who wants to keep the look of the factory radio.
http://www.eurosportvr.com/misc/ipod input/index.htm
http://www.eurosportvr.com/misc/ipod input/index.htm