Easiest to just find a FM modulator to plug your mp3 in. I have owned ones that just plug in the cigarette lighter-decent, battery powered wireless one-shitty, and hardwired one into the antenna wire behind the dash(flip a switch to turn it on)-Best.
But if you are at all electrically inclined, and not afraid to open up your radio, since you said your CD player does not work, you can actually tap into the wires that send the audio signal from the cdplayer inside the radio to the actual sound processor in the radio. Its a simple 3 wires-R,L and common ground to a headphone jack for your MP3 player. I did this in my 03 GMC with a switching jack through the signal wires on my cassette player, that way when the mp3 is not plugged in my cassette works, when I plug in my mp3 it cuts the signal from the cassette and adds sound from my mp3. If you are brave enough to try it I can give you more details, when I get around to it I plan to do a full writeup on the process. This will net you the best possible sound quality, next to having a Ipod, and Cd player with direct usb/Ipod connection, and is exactly the same way those kits at bestbuy/circuit city for adding aux input to a factory CD player works, except for $2.50 vs $100.