Change the Radio Buttons to Check-boxes Enabling Multiple Product Selection ( PHP Form)

Hi We have a Registration Form, [login to view URL] the Product is Added in the Backend and The Product is Selected through Radio Button on the Front End. We need to Change the Radio Buttons to Check-boxes Enabling Multiple Product Selection. So the Total Calculation Must also be the same Way. The Multiple Selection of Products Must be Displayed on Backend and on a PDF Generated. Eg : Product 1 - Rs.500 Product 2 - Rs.300 Product 3 - Rs.400 on Selection of Product 1 and Product 2 Total Calculation Must be Rs.800 and then Payment Process. (Payment Process is already integrated) 2. Also We have an Additional Addon Product Selection option for which on Selection An Additional Amount is Added to the Total Pricing Which is Hard-coded to the form. We need Functionality to Add/Remove/Edit the Addon Product in Backend. This is a Simple Work for a PHP Experienced Developer. We are Looking for a quick turn around time.