Buying a Former Rental Class C. How many of us out there?

Good afternoon, we recently purchased a 2016 Thor Majestic 23A from Cruise America. One of the first things I would like to do is upgrade the battery system, including the 1. battery monitor and 2. going to a lithium battery. Our unit also has some sort of small battery solar charger integrated somehow. I am having a tough time locating information on the our system to figure out how to begin- has anyone else with Majestic upgraded their system? Thanks in advance for your help.