Last year I believe it was $30 mid-week for a non-resident for the day. Don't know the overnight rates. You can either check in at the office in the main building when you arrive, or wait till they come around to your boat to collect.
In the past, I have spent the day at the beach, and come back to a bill on my boat, which I then pay in the office. Occasionally, no one even comes around, and I get off free. It's a nice marina.