I will connect the Rx and Tx pins to the Fez, but does the GND pin from the Serial cable need to be connected to the GND on the FEZ?
YES. You always need to tie the grounds together when the two devices are on the same circuit.
I thought so, but just wanted to check. I’m more of a software person rather than a hardware person.
No problem. I think a lot of people here are software over hardware