Wall/Floor fastening/assembly

Good day all. I have a 2015 178. I bought it used last September and, though all looked fine when I inspected it, I found soft floor in the rear driver side of the storage compartment under the bed when I returned from a 2 month journey through the SW. I have gradually looked at the soft floor, starting with small sections and now have the linoleum pulled up completely in the storage. I found soft and mushy plywood, removed a small section of that, inspected the underside, which was also soft, so I pulled the styrofoam on the inside and found the underside plywood also rotting. Currently, I have a box fan and ceramic heater drying this all out. I expect I will have to perform a floor repair from the back wall up to the slide out. I intend to use luan coated with g flex for both the inside and underside. I will build some additional supports internal to the floor frame. 

I understand the walls and back are supported by the floor frame and I will have to lift the wall from the frame to repair.

My question is, does anyone know how the walls and back are fastened to the floor? I would like some idea of what I am getting into so I have proper supplies or at least have a plan for refastening the walls to the floor once I get to that point. Has anyone taken any pics of the method used to fasten walls to the floor?