HAHA.. My battery won't hold a charge, how do I change the alternator?.. I guess when in doubt, "BUBBA IT".. Come on.. Are you sure your battery won't hold a charge??.. If that's the case, your alternator isn't bad. It's just that you have a bad voltage regulator. But that's assuming that the alternator is working though. But anyways, if your voltage regulator isn't working, it won't tell the alternator to charge the battery.

Here's how a typical charging system works. Once the car is started, the battery loses its charge. The Voltage Regulator sees this and tells the Alternator to charge. The alternator will put out at the most, 100amps at 14.4 to 14.6volts until the battery is charged. Once the battery is charged, the rest of the car is ran off from the Alternator's 14.4volts..

Does that make sense, I don't mean to be mean. I'm just trying to poke fun at you in hopes that you won't do a Bubba and replace a whole bunch of items until the car works.. Good luck and let me know how it goes..