We have an upcoming trip that I already purchased 8 day hoppers for. They are all registered and FP+ selections made. I just learned that we will be able to fit in a trip over Thanksgiving as well, so I want to upgrade the Hoppers to APs..
I know we can do that (I assume at customer relations outside Epcot - where we will be our first day) so we get full credit for the upgrade price to APs. ... correct?

The bigger question is one of how will upgrading the existing tickets to APs have on the already in place FP+ selections? This will be our 6th trip since FP+ went in and always seem to encounter an odd problem.. losing selections for some party members.. magically disappearing and reappearing FP+s ..

.. anyway anyone upgrade existing tickets to APs before and was there any impact on existing FP+ res?