> It’s likely it missed some crucial subtlety that will come to bite you in the ass down the line.

Maybe, but that's part of the experience of learning. I plan to maintain pools for the rest of my life, if I made an oversight which costs me down the line then the lesson will be that much more memorable.

This is an above-ground pool with a pump and a filter, the stakes are relatively low. In the absolute worst case I could rip it all out and pay a pro to do it for the price I was quoted.