I also need to change an existing FP+ (about 41 days out) to a new park. It looks like you can start with New FP, select the date and new park then you get a message 'Existing FastPass+ selection will be replaced:'
Does anyone know at what point the existing FP gets canceled/replaced? Obviously, I don't want to cancel the existing in less I can get the FPs I want in the new park.
I checked the links provided above and did not see an answer.