Note: If you have purchased BroadFast PRO less than one year before the time when you want an upgrade, you are eligible to get it for free. Otherwise the price of the upgrade is 40% of the full price.
1) Go to the BroadFast Autoresponder options page, scroll to bottom and make sure the checkbox under Uninstall Options is NOT checked. It's not checked by default, so unless you did it, you shouldn't worry.
2) Deactivate the plugin
3) Delete the plugin. You will not lose any data regardless that the text on the page says you will.
4) Upload the new zip file via Plugins -> Add New -> Upload