Is Really a no brainer:
1.Tturn the unit upside down and remove the screws that hold both halves together (3 on each arm) once removed turn right side up and the carefully remove the top halve.
2. Remove the GPS cable from the connector, Careful cause is short and move to on side of the Phantom.
3. Carefully disconnect the camera cable from the board and cut the zip tie that holds it in place and remove.
4. To install the new cable reverse the process.
Don't forget to reconnect the GPS connector back on the board when you reinstall the top half.