If the wiring harness is intact, then there should be no problem in replacing the fuses and light fixtures.
I'd recommend looking for a similar bus that's being parted out for the housings, sockets (maybe even bulbs!), and lenses. They can also be had new from a dealer or online, at a substantial cost increase.
It will be much easier to do this pre-insulating, tho I'd caution you not to insulate right up to the light housings, due to a potential fire hazard.
Sockets & lenses alone would barely
work, they need a reflector behind the bulb.
Everything should be 12V DC, so no worries there. As to what the correct fuses and bulbs are, I'd suggest you flex your Goo-Fu for the info, &/or call the manufacturer or a dealer.
PS: If you input your bus' specifications into your profile, you won't need to type that info in again. Nobody'll be able to offer an assist without all those fields filled in.