Hmm...I actually have a similar question - I have a Sony 10 disc CD/MP3 changer that uses the RF (attached directly to the antenna lead).

Now, what I'm sort of understanding is that there is a way to route it directly to the system without going via RF? I have the stock (not the rockford) system in my 2002 Xterra - and I wanted to know if it's possible. All the stuff at the link *paul had was for the 2000 model, so I'm curious how this would be done. It has it's own controller - all I'd really want is for the head unit to switch to "AUX" or something when then changer is in use.

I realize I could get a new head unit, but this changer is only a few months old - I'd rather not have to change the head unit if I don't have to. Also, I rarely listen to anything but the changer, and being able to cycle through 10 discs of MP3s is a nice feature.