Chris-
When your brushes are 1/2 life its good to change them. There are 2 sizes of bearings that go on the SA200's take these bearing numbers to a local dist and check size, older models took a wide and larger OD bearing, NTN6308ZZ. The newer models take a smaller one, NTN6208ZZ or KOY6208ZZ.
Brush dimensions when new:
T2687 1/2" thick, 1-1/2" wide, 1-1/2" long (generator brushes)
T6968 3/8" thick, 5/8" wide, 1-1/4" long (exciter brushes)
YOU DO NOT HAVE TO REMOVE THE MAIN GENERATOR BRUSH HOLDER (rack) FROM THE EXCITER BRACKET. AND I WOULD ADVISE YOU DO NOT. These 2 pieces will come off together. Once you take the cables from the generator housing loose from the brush holder (rack) the exciter bracket AND brushholder (rack) will come off together.
Leave the exciter coils attached inside the exciter housing. As far as torque specs on welder end, tighten it til it bottoms out, then bend the edge of the washer over on the nut to hold it in place.