No need to cancel your dial-up before the installation.
When you install the BB it will take you through an online registration process, at this stage it will ask you if you are an existing customer.
When you tell it that you are an existing customer it will ask for some details from your dial-up account and ask you if you want to keep your existing email addresses. Respond appropriately to these questions and the installation routine will cancel your dial-up for you and transfer your email accounts across to your broadband account.
I'll echo the
from the other guys and repeat that if you have any questions at all you shouldn't be afraid to ask.
Remember: The only stupid question is the one that
doesn't get asked.