To put it simply:
There is an "airtrain" that simply moves between terminals every few minutes. It is free and VERY simple to negotiate. BUT, it is outside security at each terminal.
I agree with the poster above concerning hotels. There are about a dozen either on or "just" off the airport grounds. All have frequent shuttles to the airport 24 hrs a day. While you "should" have no issues on the outbound, why risk your vacation? And on the inbound, you are at the mercy of customs AND the airline to make your connection...