I replaced the right hand Aux Fan in my 560sel last week. The fan was actually easy to replace after I removed the fan shroud (grille). Removing the shroud was the hard part. Here is what I did:
I removed the 3 bolts holding the vertical support rod (with horns attached) and placed this assembly down insde the bumper. I did not detach the elctrical wires from the horns.
I removed the 3 cable clamps that support the fan wires across the fhe front of the fan shroud. With a little finesse,these can be detached from the shroud but do not need to be removed from the wire cable. Pull the fan wires rubber boot loose from the shroud.
Remove the 8 "plastic rivets" that are used to attach the shroud. These are located around the perimeter of the shroud and mine were a real "pill" to get out. I broke the heads off several and had to go to the local MB House and purchase replacements. (Purchasing a few of these rivets may be step 1 in the shroud removal process. Having a few on hand will allow you to see how they unlock and you will already have the replacement part).
At this point, the shroud is loose but will not come out. The top of the shroud is hooked over the top of the sheetmetal support that it mounts to. The shroud must be pushed straight up until the inside lip of the shroud clears this support. With the fan motors protuding through the shroud and the interference from the metal bracket (that stablized the vertical support already removed), this step requires finesse and patience. I GENTLY bent the bracket out 10 to 15 degrees so that it would not interfere with the shroud being pushed up. The shroud was flexible enough to allow me to pull it out over the end of the fan motors and push it up. I had to insert my fingers through the grille area at the top of the shroud and "unhook" the shroud from the sheetmetal support.
With the shroud now totally loose, I was able to reach in and unhook both electrical connectors from the cable. Continued finesse was still required for shroud removal on my car because the shroud is wider than the opening between the left and right hand air intakes for the engine.
Once the shroud is removed, the fan replacement is easy and obvious, so I won't bore you with any more details. Reverse the process to replace the shroud.
Hope this helps. Just in case you are wondering, you can not remove the radiator and get to the aux fans and you can not obtain ANY HELP from the MB manual. I tried both.