[A4] Alternator brushes

[guitar/mcqueen]

  I've noticed that the voltage on my 98 A4 2.8 is starting to drop under load after the car gets hot. At idle in heavy traffic with the air conditioner blower on, the voltage drops to 12 or slightly under. I'm planning to replace the brushes/voltage regulator pack on the alternator (Bosch 120 amp), and was wondering if it's possible to do without removing the alternator from the car. (Anything to avoid the bumper removal/lock carrier slide routine). Anyone ever done this? Thanks for any advice.
 Gordon