Hello, and thanks for your question.
Unfortunately, you can't upgrade TSA Pre to the Global Travel (GOES) card. You would have to go through the screening process and interview again, for GOES. You sort did it backwards. When you apply for GOES and pay the fee of $100, it INCLUDES TSA Pre, but I'm sure you didn't know that at the time. However, there's a possibility that you could get that $100 refunded in the following ways:
"The Platinum Card from American Express (personal, business and Merecedes-Benz Platinum versions as well) offers a statement credit for the fee and the good news is that this fee is even refunded to additional cardholders. Plus, additional cardmembers also get lounge access with Delta and Priority Pass Select, so this can be a screaming good deal. If you have the new Citi Prestige card, you can also get the Global Entry fee refunded, and if you are a United Global Services, Premier 1K or Platinum, United will also refund you."
Read more: http://thepointsguy.com/2014/05/how-can-i-get-global-entry-if-i-already-have-tsa-precheck/#ixzz41DAx9aXD
It's worth it, if you travel out of the country frequently and want to get through Customs and security screening, faster.
I hope this helps.