a lot of decks have compositive auxilary in which is RCAs... you just buy this cheap little adapter from the store that converts a mini jack, thatll plug right into your iPod, to male RCAs.
stay away from Aiwa! bad bad bad brands... lots of problems with those I hear. The only budget brand I suggest is Kenwood.
My girlfriend has a '88 Honda Prelude, and What I did when I installed her deck was, the aux is alot like preouts, but says aux on it, so I just ran the aux lines into the tape storage thing below the hu, and hooked up an rca to mini adapter to it, so whenever she wants to play her mp3 player, all she has to do is plug it in...