Sorry for being late to the party. PTU fluid and transmission fluid changes are not "required" maintenance, but are "feel good", cheap insurance ! If you are doing it make sure to ONLY USE GENUINE MOTORCRAFT FLUIDS ! You may have to get the PTU fluid directly from the dealer, but good auto parts stores stock (or can easily get) Motorcraft transmission fluid and engine coolant.
Don't get upset about draining every drop of transmission fluid or even changing the filter. Even if you only get 50% of the transmission fluid out, because you are changing it so early, you should be fine. Transmission filters NEVER need to be changed.