For me. it was a diyer job. I bought the 2 special tools used.
a. 8mm Stahlwille allen head socket - loosen fan clutch bolt.
b. foot long metal rod - hooks in back of clutch to prevent it from spinning in order to loosen bolt mentioned in a.
Doc is at the following WEB site. For your car, they show operational theory and not actual disassembly. You can fish around for the actual process looking at other models of 126 cars - cooling system - to get the process. It's covered in one of them - which I don't know.
http://mb.braingears.com
The tools may be obtained from Baum Tools -> baumtools.com