Help Manipulating .txt Files

[JohnnyHumongous]

I'm wondering... does anyone know a way to merge a bunch of separate .txt files into one large file? Or conversely, does anyone know a way to do a Find-Replace on several text files at once?

Basically I have to do a find-replace for 3 different things in about 80 text files. Because the text files are so large and my computer so crappy, it takes up to 5 minutes to complete the find-replace on one single text file. Opening each file up and doing the find-replaces would take hours... The ways I described above would still take a long time but at least I could run the find-replace and walk away from my computer, go to the gym or something.

Any thoughts?