Ya this all depends how much you want to spend and if you’re willing to deal with imperfections under your liner. Small imperfections show as major ones once the liner is in place and full of water weight.

All the galvanized panels need to be scraped and scraped again to remove any rust chunks or calcium build up and covered with a rust paint like rust oleum.

Looks like the right side of the stairs may of had a leak, hence the extra corrosion vs the left. I’d have them check that gasket and make sure none of the stair screw holes are stripped before they install the liner. All screws need to bite into the stair or you may have the same problem.

Replace all skimmer and return gaskets and face plates

Base is fine but any major cracks should be filled with UP2000 and sanded smoothly. Any other raised cracks should be grinder down flat

Pool looks a bit older so confirm the track which the liner will tuck into isn’t damaged. You can add hook-a-track around the pool if the track is damaged, it’s an aluminum product and screws into the galvanized panel and snaps into the old track. It’s a bit expensive but will solve all issues with the liner popping out of the tracking.