Registration template with Paypal payment processing

I organize an educational conference in the Washington state every year with between 300-400 teachers attending. I'm building the conference site using CodeIgniter this year. I'm ready to start building a registration system using Paypal payments. I'm looking for example model, view controller files that I can clone and then tweak for our conference. Here are the features I need.

1. A registration page which checks user table for that user email and if it exists, then redirects to a page with name, institution for user to view and update institution if necessary. Then click to continue to a payment page with options for $40 or $50 or $60. Registrant chooses one payment amount, completes payment and it's marked as paid in the "registration" table and then the registrant is redirected to "Thank you for payment" page.
   
2. If the person's email is not in the user table, then the registration page creates the record in the user table and redirects to the page for payment.
   

I can't build this from scratch myself. I don't have enough skill yet. I just need a basic template (model, view, controller pages) that I can tweak.

Thanks for all your help.

Ron

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