Advice for aftermarket deck or iPod integration for a 2004 Pontiac grand prix gtp?

I have a 2004 Pontiac grand prix gtp and I need to get an iPod hookup to the cars sound system. I would get a cd deck but don't know how to put one in when I have the air controls on that panel and I need to keep the 8 disc cd changer. Is there a stereo converter for my car that can fit an aftermarket deck and allow me to use the air controls as well as my cd changer ? If not is there just a cord I can install to my factory unit to allow me to hook me iPod up to it without losing quality ? Any help is appreciated thanks !!!