Success! Her 2001 GP GT w/ Bose w/OnStar matches up to item #581PA11G45. This is exactly what I had in mind, an iPod interface that goes where the CD changer goes.
It isn't that it requires you to have a CD changer, it just requires you to have the head unit that supports the CD changer. The CD changer appears to be a separate add-on option from GM.
Interestingly, it indicates that if you *do* have the factory CD changer, you'll need to disconnect it, since the iPod interface goes where the CD changer would go.
It does not state whether it has a pass-through connector to plug your CD changer into, or if you would no longer get to use your CD changer. Not that this matters to me, since her car does not have the CD changer.
And with an MP3 player, a CD changer is kind of obsolete. I'm now putting around 12 hours or more of podcasts onto MP3 CDs for the Pioneer head unit in my Bonneville. It'* even easier than hooking up my iPod! Makes my commute to work and home a lot nicer.
97 SE, teflon wiper blades, Dunlop Sport A-2 tires, Leather steering wheel cover, Pioneer DEH-P480MP mp3 CDRW head unit, Pioneer 12-disc changer, iPod hookup, Boston Acoustic 3 way 6x9'*, Boston acoustic separates in door pods, Alpine 4 channel amp in trunk. Magnaflow dual outlet muffler and Ractive stainless tips. Autozone rice pipe and K&N 4750 intake kit. Clear corner lights. Energy Suspension end links.