If you didn't already know there's a command you can run to `find` files and put them in a dired buffer, then from there you can run an interactive regexp searc

If you didn't already know there's a command you can run to `find` files and put them in a dired buffer, then from there you can run an interactive regexp search/replace on all marked files. On mobile so I don't have the command names and key bindings available, but it's some combination of dired and find.