Add Facebook Login & javascript to Multicart 2.4 ecom site

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 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 a) and replace this with a user "login/register" button and pop up javascript box containing login and registration form. Also must add Login with Facebook plugin alongside this user login form. New users can register account using Facebook Registration plugin (extra field needs to be added for a username) or manually. 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. 4) For seller account, add option to "Use Facebook Profile Picture" anywhere the seller's photo appears. Auto fill with facebook profile picture if accounts are linked.