Inherited problems - please advise

[Biscuitsjam]

We bought a previously-owned bus that the owner had started the conversion process. Two things that he started:
1. The metal floor was painted with rustoleum, without any other rust treatment. All it had was minor surface rust. Do I need to take any action before I insulate the floor?
2. For a water heater, he cut a hole in the floor (2' x 1') and a hole in the outer skin on the side for a vent (2' x 1'). I want to remove the water heater, but how can I patch the outside that looks decent? (Not as worried about the floor)

The only other aggravation from the partial conversion is that he cut the heater hoses in really awkward locations prior to making new ones.

[o1marc]

Post some pics so we can see whats going on. Use sheet metal to patch the wall hole, by cutting a piece about 1" larger than the hole and sealing and poprivit or screwing it in place.
You'll probably be okay with the Rustoleum prepped floor.

[Biscuitsjam]

I can't post pictures of the floor right now - I'm on another Army field trip for a few more days.

[Mark_In_MA]

Get a sheet of similar thickness sheet metal, and just rivet it on. Apply a bead of seam sealer around the edges so it won't leak.

The key I've found to making patches look "right" is to make people think it's something other then a patch. Sometimes just painting it body-color works, other times you have to get a bit creative.

For example, get a sheet of decorative radiator covering mesh at Lowes/Home Depot. Paint the solid body patch panel black, and paint the mesh you get the body color your bus will be. Rivet them on together. The black background will make it /look/ like a vent - something that you'll find on the side of an RV/bus. If it looks like it belongs there, people won't look twice - or ever notice that the "vent" doesn't actually go anywhere/do anything.

Find something to put on the patch panel so it looks intentional - a flag, an army logo, maybe get one of those map decals of the US where you fill in each state as you visit.