To accomplish this, you'll need to remove the fan clutch, then loosen the tensioner pulley a bit to remove the serpentine belt.
The pulley you speak of that needs to be replaced is the one on the bearing bracket and a new one costs about $22 here on Fastlane. One 6mm (I think) hex bolt holds it on -- you may or may not have a plastic cover over the front of pulley to remove first. Very easy to r&r.
If you need assistance on the fan clutch and tensioner please reply.
'91 300E, 209k miles