Might I suggest an aftermarket stereo?
you might want to seriously consider that route....
Personally I have an aftermarket sound system in my 22year old
daily driver, and though my head unit isn't mp3 capable let alone dvd-mp3 capable, the 10disc changer that is connected to it IS
That changer is hard connected to the audio input jacks on the back of the head unit precisely because I kept having to change the modulator frequency to a different FM channel on long trips.
(the Sony FM modulators are user adjustable)
One of the newer "multimedia" head units that'll play either
CD's or DVD's with mp3 files would be just what you would seem to want, but a deck with that capability plus an iPod jack would be even better....
Personally I love my changer, a friend says "but iPods don't skip"
with 20-some seconds of memory buffer when playing CD's neither does my CDX-757MX changer.
I don't know if that buffer is increased with mp3 files, but I wouldn't be suprised if it was....
All I know is that if something ever happens with the 4x4 truck I have it in that makes it skip I really don't want to be inside the truck (or even nearby) when it happens