With BB you are not 'dialling up' in the telephone sense so you do not have to disable any rogue dialler software. It would be worth setting IE (or whatever browser) to 'never dial a connection' when you have BB set up. That way it won't cause problems if the BB and dialup try to access the net at the same time.
You new email address will be just that, new. The old address settings and mail will still be there but you will not be able to send mail using your old address just receive it.