I just did this on my 84 300TD- had to order a set of brushes from the only place I could find them- a M-B parts guy (who has some really cool re-engineered pieces for our cars) in Texas I believe (George Murphy I think is his name, have his catalog at home). Paid more like 20-something shipped.

But, for way less than 200 bucks for a new motor, mine too works like new.

-JAS