You're probably better off looking at something like the AudioLink or Sylfex units which you will find lots of info on on this site. The Audiolink gives you an iPod connector and an jack plug and connects to the ext CD shuttle connector on your HU. Use of the internal CD player is maintained. The main advantage of the Audiolink is that you cna control your ipod from the steering wheel controls.
The Sylfex Auxmod Advanced plugs into the MD/tape output of your HU. It is supposed to eb very good as well, the biggest problem is you struggle to get one.