Purchase Verification Capability on Website

I am looking for an experienced programmer to help me implement a purchase verification capability on my website. Specifically, I need the capability to verify physical product purchases. The purchase verification process should have a basic level of security. Additionally, I require a new payment gateway to be set up and integrate with the purchase verification process. If you have a know how of any other better and seamless process for purchase verification and if you have experience in this type of work, please consider submitting a proposal. We are a business that promotes holistic therapies and holistic living. Our product line consists of self practicing therapeutic tools that we package in what we call a tool-kit. These tool-kits come complete with tools, instruction manual and a DVD. Post purchase almost 80% of our customers demands to learn the therapy and we teach it in person in our workshops. These workshop requires different set of tools that we provide to our students when we teach them. Recently we have combined these products in a single toolkit so that now when someone buys our product they can start using basic tools and later if they decide to learn they have all the tools readily available with them. The tutorial however rather than being in person will now be online as video tutorial on our website. This is where we will need to verify the purchase and once that is done on our website the user will be granted access to video tutorial for lifetime once additional payment for tutorial is made. The user will also have to sign up using email as username. The toolkit will be sold online on our website or Amazon and offline.