I need to repair the floor on my 5000 too. I did buy a pretty good used deck but have never found the time to replace it. Yes the cab needs to come off to do it correctly. In the mean time I cut a piece of 3/4 plywood and laid on top of the deck. Been that way for several years and with carpet on top of it you really do not know it is there. The early ones had the battery in a compartment behind the seat, the later ones the battery was moved out under the step. Not sure the battery causes the floor to go away as much as the rubber mat they used and how the cab seals to the floor. Think they tend to get water under the mat if left outside and that causes them to go away. At least mine has the hole through the floor in front of the seat and the battery is behind the seat.