you'll connect an aux input adapter to the back of your head unit where your CD changer would plug in (actually, you'll unplug the pre-wired CD changer cord, which goes no where). once you have everything pluged in, you'll press teh cd changer button, and it'll displan some track info on the display (track 99, disc 1 or something) and you'll then press play on your ipod. all set.
As I understand this and I'm no expert you can install a FM modulator behind the dash. It comes with a jack plug that goes into the MP3 headphone socket. Mount the MP3 under the armrest and run the charger and FM modulator wires under the centre console so that no wires show. Tune into the FM modulator so that MP3 becomes one of the radio channels and you have radio, tape, DC multi and MP3 choices of listening.