1991 Pontiac 6000

Electrical problem
1991 Pontiac 6000 6 cyl Front Wheel Drive Automatic

i need to know how to replace the voltage regulator in my car. I went to the auto store the other day and had them test the battery, because my 'volts' light was on. They told me it was most likely the voltage regulator. I know it is inside the alternator housing, but I need assistance beyond that point. I also need to find the alternator housing as well.