You definitely want to avoid using any trains between NYC and EWR. The Airtrain is more expensive than the bus service (I think it's around $25) and the PATH train only goes to Newark Penn Station. You're then looking at either taking a local bus through the heart of Newark (not advised) or pay a cab, which will cost at least $20 because of the airport charge. The PATH also requires you to switch trains. If you're cheap and adventurous, it's an okay way to go, but not while you're in uniform schlepping your flight bags around.