You don't actually have to have a CD Changer connected. What they mean is the deck MUST BE CAPABLE of controlling an external CD Changer – not all can, even though they have what looks like a connection port on the back of the deck.
I’m not sure how to determine if yours would be able to handle an MP3 interface, other than having it tested with a factory CD Changer. If that works, then the MP3 adpater should as well. The GM9-AUX interface allows you to daisy chain the CD Changer to the unit, whereas the PXPD would not, making your CD Changer useless. Essentially, your iPod would be your “new” CD Changer.
I had a Dell MP3 player when I first installed my Pontiac Monsoon deck. There was no direct Dell-to-GM interface for this, so I needed a universal adapter that would give me an AUX input with stereo RCA jacks. I used a Peripheral Integrated Electronics (P.I.E.) GM9-AUX auxiliary input interface. This allows connection of any MP3 player through the CD Changer Aux. port on the back of the Delco player. After getting the deck into AUX mode, all control of the MP3 player for selecting song lists etc. is through the MP3 player itself. This actually worked pretty well and is about the only way to connect an MP3 player that doesn’t have a specific kit for your vehicle.

Later, I bought an 80GB iPod Video Classic. I removed the P.I.E GM9-AUX auxiliary input adapter (RCA inputs) and connected a P.I.E PXDP iPod-to-GM adapter (PXHGM1 cable connects to deck). Once set up, the adapter turns on/off the iPod automatically anytime the radio is on. It also charges the iPod at the same time.
How it works. I haven't played with it extensively, but here's what I've found. The deck "sees" the iPod as a CD Changer once you switch the deck to that function. You can still control the iPod for music selections, to set it to play all songs in a Genre for example. Next/Back, Fast Forward, etc on the Monsoon all work in music selection. I think Disk up/down functions will jump to next Playlist (I haven't created any, so I'm not sure).
Using those controls from the deck, with it's large buttons, is easier (and safer) that trying to fiddle around with the iPod control wheel.
PXDP requires a deck specific harness. PXHGM1 is used for 9-pin Delco units.

PXDPKG kit includes all 3 types of GM harnesses, iPod holder.

apps
http://peripheralelectronic...iPod_Interfacing.pdfmanual
http://peripheralelectronic...nstructions/PXDP.pdfMy complete system
https://www.fiero.nl/forum/F...2/HTML/081643-2.html------------------
3.4L S/C 87 GT
www.fierosound.com 2002/2003/2004 World of Wheels Winner &
Multiple IASCA Stereo Award Winner
[This message has been edited by fierosound (edited 11-06-2008).]