497799 Facebook Signup Integration

I need to add a facebook signup function on my existing website, so people have to choice to either register via the normal sign up available on my website ("[login to view URL]") or by clicking on the "Sign up with Facebook" button. When clicking on "Sign up with facebook" button, a JS window would popup (jQuery, perhaps), and they would be able to signup with facebook, and the fields would look similar to this "[login to view URL]" When registered, its like the [login to view URL] page, entries are inserted in the Db, and they get automatically login. We have to add some error handligns, such as 3 characters minimum and 15 chars max for the username, no username duplicates, alpha numeric only Most info about everything we need / personalization etc. should be there : [login to view URL] The 'Sign up with Facebook' button should be easy for me to add to any page on the website, by adding a few lines of code to the pages. So a class would probably be needed. I would like to have this feature done quickly and efficiently. You should also offer a guarantee for a few months so that if the feature stops working because Facebook changed something on their side, we need to adapt to it, if it's not too big of a change. Thanks !