I've found 2 companies that manufacture ipod to OEM aux stereo inputs (usually this input is for a CD changer) - PAC and PIE
Pac-Audio.com Product Details | iPod Integration for your car and More by Pac-Audio - Connecting you to the future
PAC iPAC-OEM Factory Radio to Apple iPod Adapter Connecter Cable
I don't have a PIE link handy for a 2000 GP but I think I saw a model.
I don't have the button that says CD/AUX on my stereo so I was thinking mine doesn't have the plug needed but I'm not sure - and if I do decide to buy a used delco stereo I dont know which ones will work with my steering wheel controls and amp.
In other cars I've owned I had to bypass the amp when installing the aftermarket stereo. But I also think the aftermarket head unit sticks out from the dash a good inch or so (unsure) either way if I can buy one of these AUX IN adaptors for my IPOD I'd just get that.
I was hoping someone else did this on their GP or if they could tell me which DELCO stereos I should look for ---
thanks!