Hi Ron,
I've been searching around for you, because I too didn't know an answer to this question.
It looks like your business radio with cd-player will
not play mp3 files, if you have a professional radio it would play them.
I have read some contradictory information, but I don't think it will play them.
Here is the source I got it from:
http://forums.e60.net/index.php?showtopic=22471&hl=mp3+radio+businessGood luck, and let us know if your new car is satisfactory!
Regards, Ilir