You dont need the BES if you can use POP access for your email. If you cofigure your APN settings correctly, you shouldnt have any issues with extra charges (if you do, you shouldnt have any issues getting them removed). Check this thread for great 3rd party apps: What BB apps do you have?
Enjoy. (there are probably some things I am missing as far as your set up, but nothing major i am sure) let us know how everything turns out.