Super easy to get a ticket online and once I arrived onto N Harbor Dr. from where I parked at the USS Midway Museum, it was also very easy to notice the ticket booth and where to embark. The tour guide, Rusty, never seemed out of breath or tired of his hourly repeats all day.
He made the entire excursion with so much knowledgeable detail about dozens of Navy ship seem fresh and interesting. I highly recommend doing both the north and south harbor tours.