Do these bolt straight to the existing towing mirror?

Yes. These mount at the factory towing mirror attachment points — no drilling or modifications needed. Bolt-on fit.

Will the amber LEDs work with my truck's electrical harness?

They're designed as direct replacements for the factory side marker lights, so they integrate with your existing wiring. If you're swapping from incandescent to LED, confirm your truck doesn't have load-sensing flasher modules that require resistors for proper function.

Are these waterproof if I'm running the truck off-road?

The black housing is sealed, but splash and dust specifications aren't detailed. For heavy water crossings, verify your mirror gaskets are in good shape and consider testing fitment in light rain before committing to trail duty.