Good taste - iPod + GT = less garage time.
I also have a Turbo and an iPod, and am currently using a cassette adapter. Acceptabe, but not great. The following site has an aux adapter, but as far as I could tell, you need to have controls for an optional CD changer. The cd/cassette unit in my GT doesn't appear to have this.
www.logjamelectronics.com/piechry02aux.html
If any other more electronically-literate folks have ideas for those of blessed with iPods, please speak up!