suggest putting a few mp3 flies on a flash drive, plug it into your car, follow owners manual stereo instructions - should play your music files.
no need to buy and mess with an mp3 player.
I, too, thought I would have to buy an mp3 player for car, but decided to try a flash drive first - worked like a charm, and wonder why anyone would plug a player into their car when a flash drive works.
Based on what I've read on this thread, I may invest in an MP3 player later.
For now, however, I am going to buy three or four color coded flash drives for each genre of music I enjoy, drag and drop some songs from by CD collection, maybe 100 or so songs each, and then just change the flash drive according to my mood before the start of each drive.