'03 vw jetta aux. input adapter

2003 vw jetta with the double din monsoon headunit, does not have factory sat. radio. and no factory changer. i found the factory changer cable in the trunk where the factory changer would normally be mounted, is this the cable that plugs into the P.I.E. aux. input adapter? or does it interface up front behind the radio? customer says he brought the vehicle to circuit city and they claim there is only one main plug behind the radio and no empty plug spots. awaiting a second set of tools to get radio out to see for myself. figured i would get a heads up from this forum while im waiting tho, if anyone has experience with this same situation.

never looked behind the radio itself but im almost positive there are no empty spots for any kind of input on the back. i'd just use the cd changer control in the trunk. i know the colors and their uses by heart if you need them