I live in NJ and travel to RI a bit. I would take I-95 and follow the signs for the Tappan Zee Bridge. You'll come off 95 right at the CT/NY border. Stay on I-287 and across the Tappan Zee Bridge and look for the Garden State Parkway. Unless you are well over 13 feet you won't have any trouble with the GSP.
Take the Garden State down to about Exit 129, I'm not sure of the number but the NJ Turnpike is clearly marked with signs.
The Turnpike is I-95 at that point. Just stay on the Turnpike all the way down and over the Delaware Memorial Bridge into Delaware. From that point, it depends on where you're going in Maryland.
If you have EZ-Pass it will save you a little time with the tolls.
Give a yell if I can add any more and have a great trip.
I would avoid the GW Bridge if at all possible.
