Currently, there is the type of wallboard that has a plastic surface on
it. The walls are about 25 years old in this mobile home, and I want to
replace it with some sort of wallboard that is water proof, not too
expencive and easy to install.

I'm no carpenter and I don't have a lot of money. I do have time and a
willingness to do it right.

A friend told me there is a waterproof type of wallboard that can be
used. Can someone tell me about this stuff please?

What I have now has become warped from the years of use I guess. It's
buckled out like a bulge. Between it and the shower curtain, there is
only about 24 inches left.

Thanks for any help that can be offered.