I would be happy to copy & send to you the pages out of my 1959-1967 service manual for you that outline this procedure. The 1968-1973 manual does not contain this information. I agree with Mark's above post that you want to make sure that the blower motor is indeed bad before going through this procedure!
You might want to contact Michael Medill of Mercedes Used Parts:
http://www.mercedesusedparts.com/
He can help you with the diagnostic procedure to determine if your fan motor is saveable. (Apparently on many of these motors, the bearings simply dry out, and if they haven't been burned out, they can be saved by lubricating and freeing them up) You really want to do this before spending the 40+ hours you will spend replacing the motor!
Just my $.02
Tom Drew