I have a 1994 E420 with the Bose system installed, and it was pre-wired for a CD changer. I believe that it was bundled with some other wiring on the passenger side, behind the trunk side panel, right where the trunk hinge is. I bought an Alpine changer (620 model) at liquidprice.com for less than $200, and then had it installed with a $50 adapter. The first shop I took it to had no real clue where to look, so just make sure the shop you are using is familiar with the car. Even if you do it yourself, you'll probably need to at least buy the adapter from a car audio shop, and an experienced installer will be able to tell you where the pre-wiring is. Hope this helps.