I suspect that it would be much quicker if you did some experimenting with calibre and the save to disk functionality. It would do all the renaming for you, and more, automatically.
http://manual.calibre-ebook.com/gui.html#save-to-disk
Also please note that if you change the names of books that are stored inside the calibre library, you will corrupt the library. Calibre will loose track of those books.