You are in luck. I have spent the last 6 weeks in the Newark, JFK, and La Guardia airports. I am a Union Organizer, and am helping the Transportation Safety Officers organize a Union. As a result, I am intimately familiar with these systems. When you arrive in the Newark terminal, grab your luggage and then make your way to the Airtrain (not to be confused with the airline known as AirTran). There is an Airtrain station in each of the three terminals in Newark Liberty International Airport. There is no charge for using the Airtrain, it is a monorail that connects all airport parking, terminals, and Newark Penn Station. Just take the escalator up to the Airtrain, and take the one that goes toward P4. Stay on the train after it drops its passengers at P4, and it will take you out to Newark Penn Station. At Newark Penn Station, you will exit the train, take an escalator up to the station and take either Amtrak or NJ Transit. I find NJT cheaper and easier, but either option works.

Should you decide to rent a car and drive, it is extremely easy. There is a New Jersey Turnpike exit out of the airport and the Philly area is just a straight one hour and 45 minutes south on the Turnpike. Easy peasy.

If you want any more info, just drop me a PM. I know these routes well.

All the best,

Mick