Upgrade our Facebook login to accept Facebook login 2.x for registrations

Currently the website Facebook login is working however the website used the depreciated Facebook register plugin [login to view URL] This meant a seperate Facebook login and seperate Facebook register button. The Facebook register button would take the user to another page that opened the depreciated registration plugin in an iframe. Now the Facebook login process 2.x handles the registration as well so we want to combine and upgrade this. When a user click the Facebook login button it should log them in as normal however if the member is not known to the website (i am pretty sure this is done via the email) then it should prompt them to complete a registration form, the details of this form are already taken from Facebook but the user will still need to provide a password and some other profile details. The email address and photo will be taken from Facebook. More details on the exact requirements will be provided.