04GS3

I have an 04 GS300 with the stock radio and tape player (no in dash cd), and the 6 disc cd changer is located in the glove box, but it doesn't play mp3's. I'm wondering if there is an another head unit with a cd player in it that I can swap into it's place that will play mp3 discs and still work with the changer in the glove box? Or am I dreaming?

I can't believe that an 04 won't play mp3's

I was also wondering if there was a way to put in a newer navi unit but unless I'm mistaken, I saw from reading that if yours didn't come with navi, you can't use the factory navi. Can someone confirm or deny this for me as well?

Thanks,
Joe