Remember water runs down hill so extensive ceiling damage may mean it needs to have the whole roof taken off. Water may have run down into the side walls, behind cabinets and into lower bays. Much of the wiring harness runs along the roof line and if water go to connections there and down below...a complete rewiring project?! Mold and rot...could be extensive...it could mean it is almost worthless. I'd have it inspected by someone familiar with damaged rigs. You need to determine if there is indeed wall, floor and other damage.
I guess if it were me, unless I wanted to spend a lot of money redoing the rig for an extended amount of time, I'd walk away and spend my money on something in better shape.
So, as other have said...be very careful and check out the insurance and other authorities on whether the rig can be used.
