First thing to check is , every wire/cable with an ohm meter from the connector to ground . All that show zero ohms will be ground wire/cables, that will connect to the new battery negative post.
Then with the wires carefully placed to avoid contact with metal surfaces in the battery tray plug the coach into shore power and test the remaining ( non ground ) wires for 12/13 volt feed from the converter/charger.
When you have determined the converter feed , clip the end of a 12 volt test light to the feed and touch the light's probe to the remaining wires , if the light glows dim, or doesn't light up, then those are supply wires to 12 volt systems in the RV, if the light comes on full bright you've located another ground.
99DSDP 3884, Freightliner, XC, CAT 3126B, 300 HP /ALLISON 3060
2000 Caravan toad, Remco & Blue Ox.