76 Sovereign- Updating electrical controls/ batteries, looking for advice.
I'm just getting into the electrical systems. Most appears to be working ok. Replaced the (scary) electric tape connected extension cord that was grafted onto the 30 amp shore power cable with a proper 30A plug yesterday and ran off generator while checking things. There is a battery in the compartment, but I'm guessing it is long since passed and won't take a charge. Im wanting to replace and possibly upgrade the battery system to have more power storage. I'd love to go in with a lithium ion battery bank, but don't have $3k laying around, so looking for recommendations. I've listed that along with other things below looking for advice:
1. Replace batteries- brand, size, number of batteries?
2. Most lights inside work, but old bulbs and switches on some don't work well and/or are missing knobs to operate. I don't even know if fans work. Looking for inexpensive LED (haha) replacements for bulbs and new switches? Any advice?
3. There is some backyard/shade tree wiring around the power jack. I think this ties into battery charging as well? Ideally the battery would charge when connected to vehicle OR shore power. Haven't really started trouble shooting this, but would like to. Any info on wiring, wire colors, what color goes where and the like? A good diagram would be great, but owners manual not detailed enough.