User Accounts- using passwords site-wide

[jhead]

What I need to be able to do, is this:

I have sections of a site where users create a profile.

They begin in free status, and can, if they like, upgrade to a paid status.

I want to be able to:

1) Have their usernames and passwords for the general site also work in the VBulletin forum (for all users)

2) Be able to grant them access automatically to a specific forum that is for paid users only. They will be able to pay for a paid membership (upgrade their free account) and then they will automaticallly have access to the paid users forum area.

if #2 is far beyond the scope of this forum-- then please at least inform me how to accomplish #1... in order to integrate all usernames and passwords from the main site into the VBulletin forums as well... very silly for them to have to have 2 sets of log-in info.