There is no need to uninstall the RegSupreme Pro, just install jv16 PowerTools 2005 to another directory and not over the RegSupreme.
There is indeed an upgrade option, simply go to http://www.macecraft.com/eshop/ and select "jv16 PowerTools 2005 (RegSupreme Pro upgrade)" from the list and follow the instructions.
You will need the order number of your original order to purchase an upgrade with the discount, simply contact support@macecraft.com if you don't know your original order number.