you need the premium sound system for the ipod interface... i would suggest going to
http://www.crutchfield.com -> "Outfit my Car"... type in the car info and it will show you everything that fits... i would try and avoid the crappy headunit brands though; i went with an Alpine headunit, and they are really worth the price... just know that if you upgrade a headunit, you will almost definately need to upgrade your speakers, because they will distort a LOT easier... again i went with infinity speakers... it all cost me about $500 but with every headunit and speakers you get wiring harnesses and such. if you get decent speakers then you shouldnt need an amp..
Alpine CDA-9886 (Headunit)Infinity Reference 6022i (Speakers)
also, shop around because crutchfield has a lot of specials, and some headunits come with a free ipod cord, i ordered around xmas and i got a free ipod cord with it, just browse and see what they have. If you need help, check out the live chat they have as well.