I want to hook up a disc changer to the 99' E300TD I just bought. The factory radio has a cd button, andthe original dealer window stickersays that the stereo is "CD ready"but I don't know which disc changer to get. I have been told that there should be a hookup in the trunk but I looked and don't see it, unless it is underneath the spare tire. I am assuming the factory stereo is an Alpine because the seriel number is "AL2299W0930146." Any help would be greatly appreciated. Thanks.