Add functionality to Wordpress Plugin

I have an existing Wordpress plugin to handle sales at an online store. It has several problems. I need the code cleaned up and a couple of the functions modified. e.g. Removing taxes off of products outside of Europe...Removing postage pricing before destination country is selected etc. The plugin I am having trouble with is: [login to view URL] The shipping module that accompanies it is: [login to view URL] My list of requierements are this: 1:Tax should automatically be removed from any goods AND shipping when a customer selects a shipping destination outside of Europe. (I have a list of all the European countries my client wants to ship to). 2: 18% Tax should also be applied to shipping. The plugin has no option to do this. 3: When a customer adds a product to their basket shipping and tax is automatically added, this should NOT happen as the customer does not enter their details until checkout. As I mentioned, taxes (both shipping and product tax) are only applicable to european countries). 4: The layout of the checkout page is a bit confusing. My client would like to see the cart results as: Product subtotal (without tax): Shipping & Handling total (without tax): Tax: Total: 5: The currency converter changes the currency as it should but it always leaves the Euro symbol (€) infront of the amount. Obviously this is no good if the customer is from the states. 6: At the moment a packaging slip is produced upon the correct processing of the sale but my client would like a full invoice to be able to send with the product. 7: I want to split the shipping countries into 4 zones, which Ill give to you (the client wont be shipping to all the countries in the plugins database) This is so we can apply shipping rates to zones instead of separate countries. Many thanks Nathan