Upgrading Single Park Tickets?

[ibelieveindisneymagic]

Hi All,

We are (finally) planning a trip to see the Harry Potter stuff at Universal.

I have three single park tickets (from Airmiles) that I will need to upgrade to park-to-park tickets, so we can see all of the Harry Potter world.

Where do I do this? Is there a "Guest Services" area that I need to stop at, or is it just any ticket window at the gate. Or, I've heard you can do it at Hogwart's Express ... is that true? Which is the quickest and easiest place to get my tickets updated?

Thanks!

[BrerGnat]

There are windows at both ends of the Hogwarts Express train, just before you get in the queue. I'd do it there. Otherwise there is the guest relations windows outside the park, but those lines can be long and slow.