String replacement in multiple files

What is the most simple way to search multiple text files in multiple directories for a string then replace it with another string? I have about 300 files that I need to update and I'm just looking for alternatives rather than having to edit each one by hand.

Thanks in advance!

I think I may have found the answer here:

Any other thoughts on this?

Thanks.

That sounds good to me ... pipe the output from the "find" command into a loop that performs perderabo's code on each file.

Thanks for searching first.