Database and API

I currently have a system that users register and pay through. I want to change a few things..... **1st** AA New payment processor, via API need payment and account history pages details here... [login to view URL] **2nd** Track referrer. Using user id apend the url like, [login to view URL] After registering a new user from this url, will record that user id referred them. **3rd** Query referral results page. Example User 1234 logs in, runs report of referrals and all that are 3 levels deep are displayed. That should be good for now, thanks