Check out www.crutchfield.com. They have a Farenheit DVD / MP3 player I'm looking at getting. Crutchfield is a pretty decent site to purchase from, and I haven't found anything negative on the DVD player.
Make sure who ever you go with, have them directly connect it to your system. DO NOT get it installed via FM Modulator, especially if you intend to play MP3's. Its sounds like crap through the modulator. I'm still trying get the installer to wire it in direct. Save some headache and get it right the first time (if you intend to get it installed via 3rd party)
And don't let them tell you it can't be done. llajumpvid had a great thread on exactly how to do it.