Dean, If you're worried about the walls that may still be good, once the pool is drained to ~ 1' below the break, you can cut the liner a few inches below the wall seam to be able to pull up the liner to inspect while still having the liner there to protect from weather damage This will also protect most of the floor from weather damage, just make sure that the water doesn't overflow onto the bottom. With duct tape and some plastic sheeting and a pump, you can keep the walls and bottom almost completely weatherproof.

What you want to look for is rot - your brother could tell you better than I, which which pieces of wood stand a good chance of surviving another ~15 years - in a potentially wet environment.

I agree with Tom about not doing it unless failure is imminent, but it sounded like some spots on the panels were about to give way. I'd have your brother sound the supports, perhaps you could just resheath the pool with the existing walls as they are?