With a gyro installed can we use the simple TurnLeft xxx degrees command or do we have to use the whole getGyroDegrees/SetMotor/SetMotor set of commands?

You are going to have to program it yourself using something like getGyroDegrees. The turnLeft function uses encoders in the motors.

OK. So we rewrote the program with getGyroDegree and setMotor lines, but noticed another problem. The gyro doesn't measure degrees accurately. In fact, if I check the Device Info for the gyro, the degrees will increase by one degree every 6 seconds (or so) even though the robot is stationary the whole time. This can't be considered "drift" if it's not even moving, can it? I'm thinking that my gyro is defective.

So ya what you are experiencing is drift. Usually for simple applications like this the best solution is to reset the gyro value before each turn. If this is impractical for your implementation you could try using the built in encoders for tracking rotation instead.