As far as the processing goes I just need it to find specific text in the file and replace it with some other text.
"Just", you say.
Seriously though, too bad your using Windows, as the Windows command prompt doesn't have that kind of functionality by default. If this was a *nix based operating system you could "grep" the files.
If your OS is XP, there is a command findstr
which has similar functionality to the *nix grep.findstr information
straight from the Horse's mouth (Straight from Microsoft.
For the second part of your request, changing the line, you may have to determine a line number, reading them one by one and sending them to your new file, and then when you come to the line that needs changing, make the necessary changes.
This can be done. It may not be the shortest script ever, but it can be done. I'm fairly confident in that.
Changing the filename and moving it might be the easiest parts...