Here is a picture
http://catalog.peachparts.com/ShopByVehicle.epc?q=&yearid=1983@@1983&makeid=MB@@MB@@X&modelid=300%2DSD%2D002@@300SD&catid=F@@Engine+Electrical&subcatid=F4010@@Voltage+Regulator&applicationid=000272329&mode=PA
That year also had external regulator on early chassis, so you will know when you remove the brush holder.
Pic is the reg/brush combo. Click on the pic and it will zoom out for a good look at what the brushes look like on a new unit for comparison. If the brushes are gone, you will see it and that can be both the noise and charge problem.
Simple to replace , and a common wear item.........