I recently purchased an Alpine MP3/Cd changer for my 97 S320 which did not come with a cd changer. The harness to plug to plug the Alpine into is located in the trunk. If you open your trunk and look inside, you have to remove or pull up the panel on the drivers side, under that you will find a 10 pin connector for the cd changer. Very easy install. I use it through the stock head unit and it sounds great. Only quirks are that I cant (i dont think I can) pick songs randomly and it wont play MP3 discs w/over 99 or so songs, well it will but you have to listen to the disc in its entirety from track 1. If I put fewer songs on the disk I can listen to any track I want. I paid $315 for it from ebay (new).