The motor that raises and lowers the headlights has a great amount of power. It is critically important for your safety that you de-energize it before doing any work near the headlights. (Except during the testing phases.)
The system should be de-energized by raising the headlights with the switch on the dash, and removing the "Head" and "Retractor" fuses from the fusebox in the engine compartment (in the right rear corner on US models.)
Verify the circuit is de-energized by placing the dash switch in the "down" position and turning the headlights on. If the headlights are on (they can be on in the up or down positions) or the actuators move, the system is not de-energized! Do not proceed.
You should also verify that actuators are de-energized by cycling them down and up manually in the direction indicated. This is done by taking the rubber covers off the knobs at the headlights in the engine compartment and then turning these knobs in the indicated direction. If the headlights still have power the actuator motor will jump back to the original position.
Because the complete installation is a lengthy procedure I've arranged it in steps. Between the steps, the system can be re-energized and should operate normally.