If you want the 2 special tools, go to Performance Products. Their web site is:
http://www.************************. There's an 800 phone number there. I sometimes have a hard time finding all of the MB special tools they sell on the web. The phone always works.
One tool is a metal rod about a ft. long that's bent on both ends. The shorter bend fits around from behind the fan pulley. There's a u-shaped groove it slides into. You turn the fan pulley clock-wise with a special Stahlwille 8mm allen-type socket. I believe that a long 3/8's breaker bar works best. I see them at flea markets for cheap.
As you're turning the pulley slowly, you'll eventually get it to a point where a hole in the back meets the tip of the rod and the rod slips into the hole. Now you can turn the pulley counter-clockwise to loosen as the rod has locked the pulley.
Be careful not to slip with the socket and ding your radiator.