WooCommerce shop design and implementation -- 2

We have a live website [login to view URL] made with WordPress with a simple buy now feature (later: "online shop") implemented as custom php code. We want to change to WooCommerce. Your job is to design and implement the new WooCommerce shop to the website. The new shop shall have the same products and options as the current shop. The design of the shop must be visually matching to the existing website. It doesn't need to be identical but similar. The buying process must be as simple as possible (see the current shop for reference: [login to view URL]). The new online shop must be implemented as a single page checkout process. For this, you will be give the WooCommerce One Page Checkout plugin (by woothemes). To implement the VIP / Platinum VIP options we sell, you are also given the Product Add-Ons plugin (by woothemes). The entire buying process must be very simple, fast and easy to use. We only need customer's email address and name, we do not need any other information from them (e.g. we don't need street address because we do not ship anything, we sell software). There must be a mechanism in which we can offer our existing customers (i.e. people who have bought from us before) a discounted price for our products. How will you implement this? We also need a generic discount code system, in other words, we need to be able to have discount codes which we can give out to our users. After the design has been approved by us, you will be given access to our development server which runs a copy of the live website. You will install and develop the new shop there. After we see it is fully working and approve it, you will help us to install it to the live website. The customization to WooCommerce must be done in a way WooCommerce can still be updated in the future, that is, no core WooCommerce files can be edited. The new shop must support 2Checkout and PayPal payments. Both accounts are already created and ready for use.