MR123.

Yes, the brushes are in the holder that is in the back of the alternator. The cable pulls out after you move the wire clip that secures the cable to the alternator. Remove 2 screws and you can remove the combination brush holder and voltage regulator. This is a neat design that makes it very easy to replace the brushes or voltage regulator without removing the alternator from the car.

I don't know what model MB you have but the adjusting screw is hard to get at on my 116 also. I think I used a 10mm combination wrench that could be turned only thru a small angle so it takes a lot of small turns.

P E H