Opencart Expert Needed For Small Tweaking

I have a shopping website build in with opencart. I need to do two tasks:

1. adding 4% of total amount for paypal, when customer making checkout. This is because paypal cut down 4% of fee for every business transaction.

2. every order data need to transfer on another file using variable, like order data will be send to a ftp server (2nd part is done).