Congrats on seeing that it's expensive, stressful and wholly pointless to drive a private car into Manhattan. If it were me, I'd probably drive as far as Trenton or Princeton Junction, NJ, drop the car in Amtrak long-term parking, and take Amtrak the rest of the way:

http://www.amtrak.com/stations/tre.html
http://www.amtrak.com/stations/pjc.html

Another option, if you're up for more of a driving hassle, would be to drive up to Newark Airport on the NJ Turnpike, drop the car in long-term parking, then catch the EWR Monorail to the passenger terminals, where you can get the fast & convenient Olympia Trails bus into Midtown... or on to the Newark Amtrak station where you can get the train into Penn Station.