I'm wondering if the Mac OS includes a 'find & replace' function within the OS, where I can do that for file names in a folder.

I currently use ff_remane which works fine, but I would prefer if I could do tyhis within the OS itself without having to use yet another mini application.

sudo rm -rf /

I think apple includes a bunch of applescripts for this type of thing as well. Look for "Replace Text in Item Names.scpt"