I'm posting it here instead of a new thread, since it seems like a closely related suggestion:
If this ever gets implemented, I'd highly suggest making the Search & Replace window non-modal as well. It would speed up the process of renaming considerably, by allowing to make new searches and selections on the fly, instead of closing the popup and reopening it. With the way it is now, even if you select the entire library, you still can't scroll through it to review what else needs renaming while the popup is open.