This thread may help you. The author is a great guy...
http://www.peachparts.com/shopforum/tech-help/129075-lets-change-aux-fans-w124.html
If you succeed in changing the bearings on a fan, please do a complete photo documented DIY. I have one bad fan in my basement I'd like to redo for a spare.
Rgds,
Chris W.
'95 E300D, 391K