New skimmer, screws behind liner

[overflow]

We have an above ground pool, it was here when we bought the house about 8 months ago. Last fall when I was taking down the filter and pluming a few things broke. One of them being the bottom of the skimmer unit? So i ordered a replacement but can't get the old one off. There are screws that are from the inside out that holds the thing to the wall of the pool the bad things is all the screws are under the liner where I can't get a screw driver to.

Thanks for any help.