Custom modal Log-in box with Wordpress & WHMCS integration

Hi there. We are an Internet Media Provider based in the UK and use a software called WHMCS as our billing solution for customers. As a forward-thinking company, in line with many other major media providers, what we are looking to establish is: 1. A single sign-on login / register box that is resident top-right on all of our company network pages next to other buttons in a header so that our customers can log-in to their account and manage everything online, including their own Wordpress website etc. The log-in / register box must also pop forward in a modal window against a reduced visible background. Facebook login API integration also needed. 2. A fully integrated environment compatible with Wordpress that gives customers a full 'My Account' section and will use AJAX loading capabilities to retrieve their billing and package information, offer upgrades, etc. 3. I also need a single page AJAX product ordering flow that brands with our colours and logo, thus presenting the right presence and seamless integration of all our services to customers under one roof on a single website. For more details, please contact us. Thank you.