I agree that you will not find anything relating to floor rot, although you may find a bunch of other things and decide "I should fix that since I've got it this far" Be careful, It's like a giant black hole and will suck you in. before you know it you have the whole thing tore apart.
You will have to pull it off in the area that you are replacing the floor though. there are supposed to be bolts holding the C-channel to the frame in there, and pulling those panels is the only way to get at them.
Good luck!