new liner

[CarlD]

I think you'd want to pick that up first and re-surface the sand, then lay it down again before installing the new liner.
I would also cut it up the wall a little so that the cut edge of the old liner doesn't touch the new one and become a possible source of stress and failure.
IOW, ensure the old liner on the floor of the pool is bigger than the new one.

[TMan]

My pool got those potholes supposedly from the sand washing out a bit during heavy, heavy rains. It didn't compromise the integrity of the pool but did show and could be 2-3" deep on a few. Anywho, somewhere I read to take an old bowling ball and do some diving, gently pushing the sand around them to smooth them. Of course I didn't have one and the next tip was for those of us lacking a spare bowling ball: Wrap a 3 or 5lb sledge hammer very good with a towel giving a heavy blunt side. I took that down in the pool and with very little massaging the divots were gone!

[madwil]

The divots can be from sand washing some, but can also be from uneven settling; before replacing the liner, I'd back fill a small amount of lime and smooth- lime works well to completely fill the settled spots and redistrubute weight in house foundations, assume would work well here also.
another trick used in building is to fill with mortar mix- will compress in hollows, and will harden with time to prevent erosion some... not recommended for those not familiar with concrete and/or tile beds!
Good idea to use old pool liner as a protector for the new one!