PayPal Integration and back end with log for eBook page

1. I need PayPal Integration for my website, to be able to take payments. I already have the PayPal signature and API Key. I will need clear instruction on where, in which file I need to enter these details. 2. The user will click on Buy eBook button on my website and this will open up PayPal page for payment details. 3. After the payment has come through, the user will be redirected to a thank you page. On this page there will be 3 links available for the user to download to 3 different type of files from the server. (PDF, ePub and Kindle). I would like this page to somehow be encrypted so that only this user that has paid for the eBook can download the files. 4. The buyer will also receive an email confirmation, saying “Thank you for your purchase, if you haven’t done this already you can download your files by clicking the link below”, this will take them to the page in step 3. 5. This whole process has to be secure. I would like to use Ajax for the UI functionality. 6. I will need a page that serves as a back end, this will contain a log with all the successful sold items. On each row I need the following columns: Customer Email, Date and time, Product Sent, Amount Paid (this will confirm that the files have been sent to the buyer), 7. This package has to be in one separate folder that connects to the main website so that it can be used with multiple similar websites. The folder can be called “package”. 8. A text file with instructions on how to use this with other websites should be available including MySQL entries.