While, if original, your battery may indeed need replaced, you don't need to replace it aas a means to eliminate a charge light. The battery has absolutely nothing to do with that light. Technically, you could remove the battery while running and the light would stay off. (don't do this. the alternator produces ALOT of voltage, and you don't want that flopping around in your car... DANGEROUS to say the least.)
If your intention is to refresh the car, then a battery test/change may, indeed, be in order, but not as part of your plan to eliminate that charge light.
If the light comes on during load and isn't on all the time, then its likely your alt. if its on all the time, regardless, then its likely your fuse. Likewise: if it is your alt, and it comes on at lower rpms, it is likely the diode, wiring, etc. If it comes on at upper revs, it is likely the brushes floating.
Alternator replacement isn't as hard as people may make it seem. Use the how-to, and follow it to a "t", and you'll be fine.
Ray
