Place the impact wrench on a solid work surface. In order to remove the trigger, you will have to remove the pin that also acts as a pivot for the impact wrench. Make sure that there are no holes or cracks in the work surface through which the pin can slip. This will ease the replacement of the broken trigger.
Position the striking surface of the 1/16-inch punch on the head of the pin you see in the side of the impact wrench's handle. If one side of the pin is larger than the other, then the smaller side is the side you'll want to strike.
Strike the head of the punch several times sharply with the hammer. This will cause the pin to come loose. It may require several more blows, however, for the pin to come out of the handle.
Pull the broken trigger pieces out of the impact wrench's handle, and position a new plastic trigger in its place. Tap the pin carefully into the trigger hole to prevent damage to the new trigger.
Set the pin in place once it has cleared the hole in the plastic trigger and is aligned with the opposite hole in the impact wrench. Test the trigger to make certain that it works correctly.