jeep_is_a_heep

I have a '97 grand cherokee. While driving the battery gauge is a 1/4 of the way to the left and then just drops and the check gauge light comes on. I got the battery and alternator tested at O'Reilly and the tech told me that it is probably the voltage regulator in the computer. He said I would probably have to replace the entire computer. My brother found stuff online saying you can get just the voltage regulator and just disconnect the old one and reconnect the new one and just bolt it onto the wall or something. I need some recommendations and suggestions on what to day!