Now were getting somewhere. It does sound like I won't be able to use the face of the ipod as the volume control. And will end up running this aux volume controller of some sort. The one you posted looks decent.
I hope to get going on this project after I redo some other things on the car. (Although I really should use this as my winter project, lol) So if you find other options/suggestions in the meantime, feel free to post 'em up for me. So far it's looking like I should be close to accomplishing my goal.