1) Project Details: (be as specific as possible): I already have Google Checkout on my website, I need the Notification API integrated into my website where it credits the item to the users account after they make a purchase. This could be done by using the email the user registered on my website to check the users email and update the item.
I know it sounds hard, but some people know exactly what I am talking about, how it sends a receipt back.
2) Payment method/ details (Paypal, check? Timeline?):
Paypal, Check, credit card