I didnt see why you were changing the regulator. Voltage too low/high or none at all?
The harness that connects the regulator is accessible there on the right hand side, bottom. You can unplug the old one and plug the new one in to "test" to make sure your problem is resolved. The regulator will come out easily. 2-10mm bolts and you can sneak it out from underneath or from the front, depending upon whether or not they hung yours on brackets or mounted in a frame/pan.
94-Newmar Kountry Star 40-KSDP
Spartan/Cummins 8.3C-300HP/Allison 3060 WTEC-II/25yr RV Tech RVIA Certified/Onan-Cummins Certified