i just pulled a photo of a mercedes alternator and it is just like the volvo it has a voltage regulator that is plastic and has the brushes mounted into it..

so usually with this type of alternator all you have to do is buy this assembly...

and the price was only 33 bucks so it was a good price.... but i have soldered brushes into these units as well...

i would do nothing to the alternator and only change this voltage regulator assembly... and i would do that 2 or 3 times before i went inside the main alternator.... just blow the inside out....maybe use so special electrical cleaner....