Is $20,000 to replace coping and install vinyl liner a fair price?

I have an old pool that seems to be leaking some water, especially noticeable near one corner where I'm adding concrete for a new driveway and trailer area. I dug into the area and found moisture. Below the top 12 inches, the pool wall thickness reduces significantly from 12 inches to about 5 inches, revealing what looks like thin pink cinder bricks, suggesting it might have originally been a vinyl liner pool that was plastered over. I've tried patching and using dye tests without finding a clear flow path, but I'm worried the leaks will get bigger. I was initially on the fence about filling the pool but decided to invest in it. I've already spent about $8k on upgrades including a salt water chlorinator cell, pool solar, redoing the piping from copper to PVC, and adding a pool lift for accessibility as I use a wheelchair. We've had the pool for 10 years with few major problems until recently. I'm hoping to use it regularly with the new lift, as I believe lack of use contributed to it turning green previously (clarity improved dramatically with a used vacuum). I'm considering this option to address the potential structural/leak issues and make the pool reliable for regular use.