Magneto Coupon Codes

I am about to launch a new product and would like to send a physical gift card to each new customer with their first order entitling them to $5 off their next purchase with us. I wish for the codes on the cards to be individual so that they cannot be shared and spread around. I have a magneto website I need someone to -generate the unique codes to be printed on the cards -ensure they are programmed to work with the website checkout -tell me how to know whether an order is from a new customer or an old customer, to prevent the gift cards being sent out to old customers In your reply, please let me know if this is possible, and how you will go about doing it. I am looking for someone who is knowledgeable and intuitive for ongoing work if this project works out well