After opening the trigger housing, one of the things you can do is replace and remove the trigger mechanism. It's as simple as getting the housing open.
Use the socket wrench to remove the 0.5" length screw from the bottom of the handle.
Separate the cord from the handle.
Locate the two wires attached to the black trigger.
Pull the wires out of the trigger. It may take a bit of force.
Push the wires into the new trigger piece.
Make sure the wires go back into the correct holes.