Converting my page to accept nochex instead of paypal

Currently my website is accepting paypal, I want this changed to nochex. There is no shopping cart, it is one page with 5 or 6 "purchase" buttons which take you straight to paypal. Users are purchasing credits for use on my website. This is what happens currently: -User presses the purchase button next to the credit option they want -They are redirected to paypal and they make payment and are redirected back to my site -The credits are automatically added to their account on my website (assuming the payment was successful, and waiting for e-cheques to clear) -The transaction details are recorded in a transactions database. -I am sent an email confirming a new credit purchase with their username, email address, and amount purchased I am fed up with Paypal and want the same process but with nochex. You will be required to: -Change the processor to nochex -Ensure that the above process is followed (you will need to write your own processing script to add the credits and the records to the databases) -Ensure that there is no way that users get credit without paying! It must be secure!