You can change the brushes without removing the alternator, but you must remove the regulator/brush assembly from the alternator. This is held on the back of the alternator with two screws. Remove the assembly to the bench.

I find the easiest way for me to remove the old brushes is to drill them out. I use a flat file to file the surface of the solder joint smooth. This gives a little more definition to the "target" area as well as providing a good surface to get the 1/16" drill started. Since the solder is soft the drill follows the path of least resistance removing the solder/leaving the holder intact (you will be drill towards the brush in each case). Once the solder connection is drilled out the old brush is released and basically "pops" out due to it's spring load.

I apply paste flux to the lead of each new brush. If you have trouble getting your solder to "stick" or flow out it is most likely because of the lack of flux. The new brushes from Volvo (part number 1362710- less than $4; includes new springs) have a solid wire lead on them that makes it easy to "thread" them into the brush holder. Pull them down far enough that the sides of the brush holder support the brush in an upright position. At that point bend the woven wire at a right angle to the holder to keep each brush positioned properly.
Apply the heat of an iron to the junction of the brush holder and the woven wire. Take a relatively small diameter piece of solder that has been dipped in the flux and touch it to the brush holder where the woven wire exits. Use enough solder so that the drill hole fills in around the woven wire (don't get over zealous here you don't want solder dripping out the backside into the brush holders). Trim the excess wire off and reinstall the assembly. Be sure to tilt the assembly as you position it so that when you press the assembly into place the brushes are pushed back down into the brush holders.

Randy