Audio Systems: 01 VW Jetta ipod adapter choices, stereo tape player, vw jetta

Question
A friend has a 01 VW Jetta with the factory single DIN stereo (tape player only) and a factory 6-disc CD changer in the trunk. He wants to add an ipod adaptor that will work with thru a factory HU (no aftermarket headunits).  I've done some light duty work like this with many of my Volvos but am unfamiliar with VW radios. I know we can buy a USAspec ipod adapter but it connects to the OEM HU via the 6-disc plug so that would eliminate the existing changer which isn't desired. I was thinking if we could pick up a double DIN HU with a single disc in-dash player that would work but I can't find anywhere if VW made such a model that wasn't the upgraded Monsoon system which would require install of an amp and possibly new speakers (too much work for me and cost for him). If there is a lower HU that I can swap out I would go with the USAspec adapter.  Can you confirm this and the model numbers?  I've been searching all morning and can't find any data on VW HU model numbers.  If not, any suggestions on how we can hook up an ipod to the factory unit without RF transmitter (too low quality)?  Thanks in advance.

Answer
you can keep all the factory system and install this in the back of the radio, installation is simple and only takes a few minutes  

http://www.oemautosound.com/pc-346-143-pie-x3-vwr-audi-triple-input-auxiliary.as...

you can also add the ipod charging cable  
http://www.oemautosound.com/pc-353-143-ipod-docking-to-rca-charging-cable.aspx