Custom modal Log-in box with Wordpress and WHMCS integration

We are an Internet Media Provider based in the UK and use software called WHMCS as our billing solution for customers.

As a forward-thinking company, in line with several other major media providers, what we are looking to establish is:

1. A single sign-on register/ login box that is resident top-right on all of our company network pages next to other buttons in a header so that our customers will log-in to their account and organize everything online, including their own Wordpress website etc.

The register/ log-in box must also pop forward in a modal window against a reduced visible background. Facebook login API integration also required.

2. A fully integrated environment compatible with Wordpress that provide customers a full 'My Account' section and will use AJAX loading capabilities to retrieve their package and billing information, offer upgrades, etc.

3. I also want a single page AJAX product ordering flow those brands with our colors and logo, thus presenting the right presence and seamless integration of all our services to customers under one roof on a single website.

Skills required are AJAX, CSS, HTML5, WHMCS, Script Install