Will this switch work with my existing door panel, or do I need to remove it?

You'll need to remove the door panel to access the switch housing and unplug the old unit. The mounting points are factory-original, so the new switch slides in without modification.

Does this come with the wiring harness, or do I reuse the old one?

The switch assembly includes the connector. You'll unplug the old switch from your truck's factory harness and plug this one directly in — no splicing or adapters needed.

What if the windows don't work after I install it?

Test the switch before fully reassembling the door panel. If windows still don't respond, check that the connector is fully seated and that the vehicle battery is connected. If the issue persists, the problem may be upstream in the door wiring or motor, not the switch itself.