The McNamara terminal and North Terminal are completely disconnected. The tram in the McNamara only serves the A concourse to enable people to get to the 'far' gates quickly from the central link.

To get to the North Terminal, you have to exit security and hop on a shuttle bus that runs pretty regularly. (There are a few). Be sure to pick up the bus on the lower lever of the parking garage--Not the Westin location. (If you go to the westin location, it circles around to the parking garage location before going to the the North.)

To be safe, Figure 15-20 minutes each way, including possible wait time. Your GE interview should take about 30 minutes so you've got plenty of time.