Remove the battery negative cable.

Once you have removed the old brush/regulator assembly, inspect the commutator for excessive wear. Do this with a mirror, a strong light and rotate the alternator pulley in increments. You will have to loosen the belts.

During installation you will need to retain the new brushes in their holder with a small drill bit. Once the brushes clear the edge of the commutator , the drill bit is removed.

While your at it, check alternator ground wire, bushings and belts. Also the wire to the oil pressure switch for insulation damage or breakage at the connector.