To add a bit to Bill's advice
, the York River Yacht Haven is a very good marina, located in Sarah's Creek on the north side of the bridge. There's a really good restaurant there, as well.
I've never berthed at Riverwalk, on the south side of the bridge in Yorktown, but the docks there are normally populated with boats of various sizes, power and sail, so there must be a way to arrange for dockage. I wouldn't recommend anchoring
in the river unless you feel assured of fairly calm weather
for the duration--it's wide open, with no protection.