The path takes you to the 911 memorial. We did it twice. However we liked the ferry. Much more scenic, but there is walking involved. If it's a nice day it's not bad. The path however gives you a transfer so you can take the NYC subway to Times Square.
The ferry to liberty island and the Statue of Liberty is also right there. You do have to take a ferry across the harbor to get to it, I think it's $3 to board and cross to the other side.
If your not at your RV all day the gray tank should last you a few days depending on the size of your tank. I don't belive there is a honey wagon, but they do have a dump station.
Here was the view from our spot!