Paypal integration and changes to existing website

I have an existing website [[login to view URL]][1] and require a few changes: * PayPal Digital Goods Express Checkout integration - I would like to integrate this payment solution with my current site. It currently uses PayPal but is not very user friendly * Secure download functionality for digital product after payment processing * After the payment is processed the customer has to complete an Aweber form so they receive all of their product, on submit I would like the download to commence. * Help me find a solution to include correct tax in price only when user is from a specific country e.g. Australia only * Make the page that the customer returns to after payment processing a secure page * Add PayPal buttons to pages * Make updates to links as per changes implemented (where appropriate) * I am also finding that the site is blocked sometimes and I do not know why e.g. a company using websense filter blocks the site I am looking for someone who will help me come up with the right solutions for my needs and to ensure the best customer experience. Here is the developer guide for the checkout. [login to view URL]