upgrading tickets

[jcanary]

I want to upgrade a ticket that I have which is a 2 day plus 1 that expires 12/31. I want to get one of the new MYW ones for a 3 day hopper. Is there a place in Downtown Disney that I can upgrade or is it only at the parks customer service windows? If there is one in DTD can someone tell me where it is located?
thanks

 

[Cheshire Figment]

There is a Guest Services in DTD Marketplace. It used to be next to Once Upon a Toy, but it moved a few months ago. I think it is now near Ghirardelli Chocolate.