oh man take that battery killer to the dump and replace the whole power centre. I had one like that in my camper when I bought it and it came out and a proper PD 4000 series went in to replace it. fairly strait forward, since you took it out you have a clue. I took the opertunity to upgrade my battery cables and such while I was at it as I also moved the battery location.
I went with this one https://www.progressivedyn.com/pd4000-series/ as it was close to the original size and I only had to make the opening 1" bigger.
Steve