No sweat there, it will simply be a cost at a fixed rate of 20% of the store price. You may add the product you wish to upgrade to your cart and at checkout it will indicate an upgrade price. Alternatively, you may click on your user profile and directly upgrade through your ‘Order History’ or ‘Inventory List’.
When you visit a content detail page, you may see a ‘Non-Exportable’ icon (shown below), in which case this product can only be used in Reallusion native environments of iClone or Character Creator. Similarly, you will also see an (iContent) tag in your shopping cart indicating it is non-exportable.

You are authorized to sell rendered images and animation videos for commercial purposes, so long as the purchased Content is part of a larger work that substantially changes the creation. However, you are not permitted to sell the creations in the stock websites such as Shutterstock or Envato, or in any dynamic media library.
You are authorized to use the “Output” images for the 2D print on physical products, such as packaging materials (e.g. boxes, books, caps, t-shirts, stickers and so on). The 2D-printed physical products are permitted for commercial purposes.