When using the Navx does it have to be in the center of the robot to work properly? Please share any resources you might have. Thank you.
No it does not. Just make sure you zero it correctly.
From NavX Best Practices
9) If possible, mount the navX-sensor circuit board near the center of rotation
Since navX-sensor measures rotation, errors in the measured angles can occur if the navX-sensor circuit board is mounted at a point not near the robot center of rotation. For optimal results, the navX-sensor circuit board should be mounted at the robot’s center of rotation. If the navX-sensor circuit board cannot be mounted near the robot’s center of rotation, small amounts of error that may be noticeable can occur.