The work continues! I have sealed a few more places where the fibreglass topper connects to the van body where I think there was moisture coming in. I’ve also ripped out all the old shag carpet from inside the storage areas and under the cabinets (that might have been the grossest thing - glad I wore a respirator is all I have to say about that!).
I also bought the new battery and connected it, which wasn’t as scary as I thought (electricity kind of scares me).
Next steps are going to be to get some new cushions made, and build the toilet compartment and the storage in the back!