Parking, I'm not sure but I can shoot Universal support a message about that for you. I know you can reenter the park with no issue though. I've gotten food at CityWalk and returned before.
I've definitely got a packed day today. This, whatever MMS offerings I can see, and the final day of a longtime Deacon Actor's performances at Waterworld (Greg Dolph) are in it for me today. The last thing is why I'm at the park today, but I definitely didn't expect the ride to begin rehearsals at park opening.