DIY bottom repair questions

OK....so I have a liner pool 18x36, 8 foot deep end...pretty standard. Long story short it is at this moment it is a wrech. Loner is in tatters and the bottom has been affected by rain, plants, and the like. I have called around with much dismay (and outrageous prices) for a company to do the replacement, and at this point I am looking to do it myself. The liner does not seem to be the big issue, but the bottom repair may be. It is sand in the shallow end and appears to be a sand/concrete mix down to the deep end. It is very rough and in the edges there are areas where it has washed out below the wall line. Should I do a skim-coat in vermiculite over the whole thing? Just smooth the sand? I will post photos if I get approved. Also any recomendation on liner companies? I have come across many with proces ranging from $795-$1400. (the mil does vary). I am trying to do this as economically as possible, but not something I want to have to redo in a couple years. I also have a well pipe (for the groundwater) any suggestions how to best handle that? Much thanks in advance

Stephanie