On one of the Russian Parts sites all of the little Bushings, Bearings show up in the Parts Catalog.

That does not mean Mercedes sells all of them but there is a good chance as there is no major electrical damage someone can fix their own Starter.

Getting the Starter off of the Car seems substantially harder than taking the Starter apart.

It could be the OP's Starter simply needs a good cleaning.

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84 300D, 82 Volvo 244Gl Diesel