If you can get your hands on a copy of Renamer4Mac, I would highly suggest it. It has been bought up by another company and the name of the program has been changed to simply 'Renamer'. I believe it cost $30. Renamer4Mac was substantially cheaper than that when I bought it - $6 or $8.
In this video I show how handy it is to change the name of whole folders of files in one fell swoop.
