All your answers here, including how to buy a premade harness:
www.thenewx.org

FOR SALE - [MPS] Overide M226 e-Locker - PBR
FOR THE WIRING MOD..... You will need to access the Wiring Harness at the Differential Lock Control Unit (DLCU). It may be easier to do this by removing the Driver-side Door Seal and the Knee Knocker Panel under the Steering Column. Perform the changes on This Schematic. Due to new security...