Paypal and Google API Integration

No Automatic Bids Accepted! Website sells downloadable product (digital product) and has an order form with submit button. On submit, the form checks itself and goes to an order page with a Paypal button. What I need is for there to be a Paypal and Google Checkout button on the initial order page. Once the visitor fills out the order form, they select one of the payment methods. When they click on either button, the order form information is sent to me and they proceed to the Gateway payment page. Once payment is made, they are automatically taken to a secure, temporary download page to get product. If the visitor is on the payment page and closes the window before completing the payment, there should be a popup offering a promotion. Clicking on it would then take them to the order form with a reduced price. You should be familiar with Paypal and Google checkout API.