One of those puzzles where I turned the air blue while solving the frustratingly elusive clues but was left with nothing but admiration when I'd finished. Is Check a new IQ setter? If so it's an impressive debut. I have zero interest in the theme elements but that didn't matter, and it's always satisfying to have grid changes result in real words, which cuts down the grid-staring, Also the endgame leaves no doubt, unlike some recent puzzles.
I didn't like the down clue starting Tear down... because for me the instruction "replacing one with another" doesn't quite work grammatically, even if the intent is quite clear. I'd have preferred the implied "one" at the end of the clue to have been present. But that's probably just me.