Adapt Drupal 7+Ubercart 3 to deal with specific kind of digital product

I want to create an e-commerce using Drupal 7/Ubercart 3 to sell digital products, like gift cards, but instead of shipping the card we will sent the code by email because this is just what the costumer needs and this way we can offer instant delivery. Here is the thing: when I create a product, I need to specify how many items there are in stock, each item corresponding to one code. This code must be hidden until payment confirmation, so it will be sent by email to customer and the code will be removed from database, and the stock decreased by one. I was unable to figure out a way to get Ubercart to work the way I need using just Drupal modules, so I need assistance of professional who knows how to accomplish this either by using an existing Drupal module or by coding new stuff. If you will apply for this job, please tell what you understood I need using your own words and explain what you think is the best approach to solve my problem. If you have any doubt, please ask me BEFORE telling what you plan to do.