Try browsing some of those threads; they should provide more than enough to get you started, if not providing the exact solution you need. If you still have additional questions, it's probably best to reply in one of the existing topics (the one that seems closest to what you're trying to do), instead of continuing this thread.
Don't forget that you can do simple renaming directly in the Finder. Select all the files, File -> Rename... (or control/right-click the selection and select Rename...) and: