It has two changes. A letter moved in from the previous across, and a letter moved out to the next one.
I’ll give one example to start you off. For 27a, the wordplay leads to WOO + LP + SACK*. An F is added from 25a, and an O moves into 30a, leaving a new word as the answer.
This is a tricky puzzle, to be sure. No shortcuts, and the spelling of the theme doesn’t help much until you have a pretty full grid.
Hope that’s not too much information