One more question: what exactly am I getting with the pro-bundle?
Exactly what's stated here for one blog and for one year > http://en.support.wordpress.com/bundles/
And am I too late to get my money back if I decide to just purchase the domain?
WordPress.com provides a 30-day refund on all upgrades except Domain Registrations, Domain Renewals, and Guided Transfers. Provided you are logged in under the same username account that purchased the upgrades, you can request a refund yourself directly from the Store section of your Dashboard
Note: The refund can take 1-2 weeks to post back to your account.
If you want to cancel the non-domain upgrades in your Bundle, you can do it via Store > My Upgrades. Click on "Cancel and refund", then select the option to cancel the Bundle and keep the domain.