That's really tough and I'm sorry to hear that happened. Lots of reports of flooded parks and campgrounds.
First thing - do you have insurance that might cover it? Seems obvious because I'm sure you would have checked with the ins co but thought I would ask. Like wyo700, I would have thought it'd be totaled if water covered everything except the AC for 2 full days. Was it really covered? I would have expected the water to effect the various electrical systems but those appear to fine. Not that you need more issues to deal with.
As for the water heater and anything in the water system, I think you have to assume its been compromised and needs to be disinfected. This would be similar to what you have to do when dewinterizing. You would typically fill your fresh water tank with 1/4 cup bleach for every 15 gallons of water, run it through the system including the water heater, let it sit for half a day, dump, and flush with fresh water. I'm not sure how you do this if the FW tank is wrecked.
You asked what else needs to be removed so that mold doesn't appear. I really don't want to be the bearer of bad news, but the thing is I'm not sure this is possible if it was actually submerged.
Walls and floors in a travel trailer are not made to be waterproof and the material used to make the structure might now be soaked through (I imagine).
I am unfamiliar with your model, but today's Surveyor trailers use fiberglass over aluminum framing and attached to the cross members is something like luan and then filled with insulation. If the luan and insulation are wet, then I am not certain it can be dried out enough to avoid delamination and mold. You could try running dehumidifiers for awhile and see if that helps.
I'm really hoping this can be taken care of through insurance.
If not, maybe some of the other members here have other ideas on how to make this right for you.