Well, the FM modulator is one (known) option, an aux input (maybe by emulating a cd-changer) is another.
On the second matter, it depends what kind of adapter you use to get to rca. I have cables that are separated, right in the mini-jack connector, so I will not notice much interference from the other channels, will I?
Either way, welcome to the forum, and thanks for that helping spirit (much better that those people posing 1000 questions in their first post, with answers just a search away

)
Joa