This is a very simple job, although getting to the screws is a little tricky.  The alternator brushes and regulator come as an assembly.  There are no wire connections to the assembly.  Two phillips head screws hold the assembly in place.  The rear screw is easy to get to with a standard #2 phillips screwdriver.  Access to the front one is more difficult, as the oil dipstick tube, knock sensor and various wiring harnesses get in the way.  I found it helpful to remove the two 10 mm bolts that secure the top of the dipstick tube.  I then removed the upper bracket and the dipstick/cap assembly.  I DO NOT RECOMMEND TRYING TO REMOVE THE DIPSTICK TUBE, as they get brittle with age (I don't even know whether it is a press fit or a screw fit into the block - I just left it alone).  Removing the upper bracket allows the tube to be bent fore and aft enough to allow a bit better vision and access to the screws.

I replaced mine at 118 thousand miles.  There was about 1/8" left on one brush and about 3/16" left on the other,  New brushes are between 1/2" and 5/8" long, so mine were getting pretty close to the end of their life.  Another consideration is that when they get that short, the brush spring tension probably isn't as high as it should be.

The brush/.regulator assembly is at the bottom of the alternator.  Look at it from the opposite side of the car to get a better view.

bulletRemove the screws and bracket at the top of the dipstick tube, as described above. 
bulletUsing a standard #2 phillips screwdriver, remove the rear screw that holds the brush/regulator assembly.
bulletYou can try a stubby screwdriver on the front screw, but I find that I can never get enough torque with a stubby driver.  I used a ratchet with a phillips screwdriver bit
bulletYou can buy socket/screwdriver bit sets, or you can use a bit in a 1/4" socket.  If you use the latter, wedge the bit tightly into the socket with a bit of paper - or rubber cement - or anything to keep the bit from falling out.
bulletRemove the front screw, then pull the assembly out, rotating the bottom out first.
bulletInstall the new assembly.  Stick the brushes in first, then rotate the bottom of the assembly in to compress the brush springs as the assembly goes into place.  There is no need to use anything to pre-compress the brushes and hold them - just rotate the assembly into place.
bulletInstall and tighten the two screws.
bulletRe-install the dipstick tube top bracket and screws, and the dipstick.
bulletClear all tools out of the engine compartment, start the car and check the voltage.