A bit tight but you should do OK replacing it. On my car (93 300E) you almost have to remove the fan and that can be slightly difficult. On my car, there was a tensioner and a separate shock for it. I think on the newer 104s, it is together in one unit. It is located at the front of the engine and is one of the pulleys that the belt goes around not too far down from the top (just enough to make it interesting changing!). I think all of the other pulleys drive something but this is just to give the belt tension so you can probably pick it out without too much of a problem. This is one thing that is in the MB CDROM for the 124 series and I assume it about the same for your car. If you need it, I can probably e-mail you that sheet out of the CDROM.