Build a Web page on an existing website

Before you bid, Please read the description carefully !!!! The website you are going to work is [login to view URL] This is already a complete website and I only need to add some part. I need to add a page which is similar to shopping cart page of ecommerce, please read the instructions: Instructions: 1. This is a already complete website, and heavily coded. I don't want to change the existing code structure, only add a web page. To do this, you need to fully understand the structure of this website.( you need to understand php classes, functions, javascript, ajax to work on this ) 2. Login/sign up and administrator page are all created, you don't need to work on this. 2. As you can see, on the first page, if you click on the "Classes " on menu, you will be directed to a page where you can see four types of classes. For every type of classes, there is a link named "view details". But this link is not linked to any page, I want to add a page to this link, if they click "view details", they will be directed to the page you created. 3. On the page you created, people will choose between monthly and trial version of that type of class. For every class there are four locations they can choose (This is hopefully a dropdown menu). Under the page there is a map, which changes according to the location people choose. 4. After people choosing the classes, then they will be able to proceed to check out using either paypal or credit/debit card. (price will be calculated according to what people choose) Again, please read carefully before you bid, and I don't want you to change the structure of the current code, which means you need to fully understand the code. Thank you !