Custom API work based on existing code

#1. I have a site that is 95% code complete, just needs the form modified a bit to everything working. #2 I have new website that I'd like to have the same API call but using different styled content. Essentially, you will see working example of correct API calls flow is api db lookup, return results, payment processing via paypal, return PDF results. The code is there, just need it altered a bit for each site.