Add Facebook Login API and javascript to website

I need a programmer to add Facebook login and add Javascript pop out box to the registration process for my Iscripts Multicart 2.4 e-commerce website. Programmer must be an expert in Javascript and experienced in integrating FB features. Must be particularly neat in architecture and file use. (i.e writes new files as opposed to 'spewing' involved logic over many different existing files.) The job... Current website has two ways for users to login or register: a)User login form and register now link in header. b)[login to view URL] page (user directed to on checkout if not logged in) User must click "register now" and fill out USER REGISTRATION on [login to view URL] for a basic account to buy products. Information provided: a username, email address, name and password. 1) Instead of clicking "register now" and reloading to separate [login to view URL] page, I'd like programmer to remove the login form in the header and replace with: One user "login/register" button that uses pop up javascript box containing login and registration details below: I don't want to show all fields in the same pop up at the same time. First view is: For user login I'd like for fields -Username/email - password On New User side I'd like -button for “register now” -or register with facebook Second view...On click “register now” reveals all fields below in same pop up on user side -first name -last name -username -password checkbox for receiving updates If user chooses Facebook Registration an extra field needs to be added for the username. 2) Add Facebook Login plugin and Registration plugin to [login to view URL] page. 3) If user is logged in the [login to view URL] page can not be accessed if URL is typed into browser, and is instead redirected to the homepage. I want to make sure that if someone is already logged into their account, they can not register a new user account unless they have signed out first. Currently in the software a user can register a new account while still signed into their old account. 4) For seller account, add option to "Use Facebook Profile Picture" anywhere the seller's photo appears. The current profile picture is stretched to fit into a square shape. Please could you make sure the correct aspect ratio is maintained. 5)her changes to [login to view URL] On [login to view URL] when user clicks on the large main image I'd like a larger version of the image to display in a pop out javascript box, rather than current system where the same sized image pops out in a new window. This is so users can see the item in more detail. 6) Also I'd like a “More from this seller” selection of up to 9 images. Similar to example shown on the left sidebar on [login to view URL] Users can click through to the item listing.