Alternator Failure, what should I replace?

'94 Camry 4 Cyl. 77k mi.

I strain my alternator with a stereo system. It held up for almost 3 years, but I think it's finally starting to throw in the towel.

The voltage out of it today was only 13.3, turned the headlights on went up to 14.4, turned the high beams on, went down to 13.7. Wipers made it 14.6...13.7..12.9...13.3. Basically everytime I change the load on it the voltage changes, the wipers made it go crazy, but eventually it steadied at 13.3

The obvious answer to me is the regulator. I figure I may as well do the brushings as well. Should I also replace the rectifier bridge? Or am I going too far already and should just start with the brushes.

I tried to understand as much as I can from the FAQs on rebuilding the alternator. Is removing the pulley really necessary for this job? Or can I do the above 3 without doing that, I understand it's hard and I won't be able to do it without an impact wrench... which means I won't be able to do it.

Any other tips would be appreciated as well!

Also an idea on how much this is going to cost me will also be greatly appreciated. I have 4 hours between classes tomorow, hopefully that will be enough time to get it done.

Edit:
Diagnotstically the only thing wrong is that my battery doesn't seem to be getting charged and the voltage is irregular. I do not get lights on the dash indicating failure. I also conducted the screw-driver test where you see if the alternator works like a magnet, and it didn't in the slightest. I don't know how reliable that test is.

What was it that made you measure the voltage output? Are you seeing dim headlights or the like. Voltage variations with load changes are normal. It shows the regulator is doing it's job. Let the car warm up and measure the output with everything turned on. As long as you see at least 12.5 vdc you're ok.

On second thought check the output with everything on except the stereo. Should see at least 13 vdc. Now turn on the stereo. If it drops too low you might want to consider an uprated alternator.

I always check my voltages because I'm always having to charge my battery. I used to have an Interstate wet-cell battery I had to fill and charge every month, then it turned into every week, then it wouldn't hold any charge.

Got Optima Yellowtop, had to charge it every 3 months, now it's looking more toward it needs to charge every month.

With the car running my alternator always used to put out 14.5 without the stereo on. If I turned on headlights, or anything else, it would drop a little, then come right back up to 14.5. Now it stays mostly at 13.3, but has different voltages for each load.

My stereo used to be the only component that could give it swings, between battery voltage and 14.5 with the beat. Now my wipers give it voltage swings between a little over battery voltage and 14.6.

I also judge when to test voltage on how well the engine runs. As the battery dies, the engine starts to run sluggish. I charge the battery, and it will run fine. The engine started to run sluggish, thats why I tested.

With my stereo on the voltage drops below 12.5 for certain hits. It used to drop to 11.5 on the wetcell.

Edit: I just rechecked it again, couldn't check with stereo cuz its 3 AM. But now it's at 14.7 constant. No matter what load I put on (even power windows), never dropped below 14.62. This is with the engine cold though, so at 1k RPM. In the morning I'll be able to check at warm 800 RPM

Is it possible for the alternator to be "overheating" and letting it sit returns it to normal?