I am having a hard time seeing anything useful in that picture. Some if not most connections are to be found along the outside wall. Often there will be some sort of access panel on the outside.
Gas lines and wires typically run along where the floor and wall meet. So the connections will be there. If there is an access available in the outside wall it will be much easier to use than trying to get to them from inside the camper going through the cabinets.
However sometimes they will be under the front cover inside if there is a removable front cover.
Mine is totally different model but outside wall below fridge
vent has a door that opens to access gas lines and wires. I seem to recall fridge is screwed or bolted to the floor also.
is an antique. But for what it is worth the front cover comes off and the connections are behind it. Will also probably have an exhaust vent or something that acts as a "chimney" for combustion gasses that will need to be disconnected.
I don't know if one can remove the cabinets with the appliances in them as I think you described. Appliances should be removable without pulling cabinets. One would at least hope they didn't build the thing around an appliance.
The ones I have seen appliances only have a trim piece with a couple of screws going into the cabinet. Just to keep them together not the main anchors for the items. Only way to screw to the fiberglass is to attach a strip of wood to the back side and put screws into that. Not able to handle a whole lot of weight
Wish I could be of more help but go on the outside and see if there is an access panel for those appliances.