Concrete in vinyl pool too hard

[LindaE]

My liner needs replacing. 2nd one in nine years. Pool leak detector guy says the concrete bottom is too hard (someone cut corners so that it would harden faster when it was built) and this is causing the kreepy and pressure of the water to make hundreds of tiny holes.The same thing happened to the first liner, which the original owners installed, and it was only 2-3 yrs. old. The second liner, which I had installed, was a 30ml. and lasted about 6 yrs. He says the bottom needs to be resurfaced with a softer concrete mix so this doesn't happen again. He also said that I can do this myself to save money, and he is willing to show me how. Also, I can save money by doing the liner before spring.(He will give me a discount if done before Mardis Gras)
I have a few questions. Can a liner be replaced in winter (south Louisiana) and is this concrete thing a huge factor?
I need advise because I am toying with the idea of filling the thing in with dirt. (My husband & I are 60ish and don't use the pool much.)
Another question-- I am concerned about the age of the plumbing (pool 8-9 yrs. old) and don't want issues with that if I replace the liner. Do heavy concentrations of chlorine deteriorate these pipes when the pool is heavily shocked? I have already fixed major cracking in the skimmer with that underwater epoxy, but that seems to be holding quite well.
I hope I didn't ask too many questions in one post. This is new to me. Thanks, Linda