Will this plug directly into my truck's existing mirror wiring?

Yes. This mirror uses factory mounting points and OEM electrical connectors — no adapters or rewiring needed. Plug it in and it powers on.

Do I need to remove the door panel to install this?

Door panel removal is typically required to access the mirror mounting bolts and electrical connector. Plan 30–45 minutes if you're comfortable with basic panel work. A Torx bit set is your main hand tool.

Does the heater work independently or only when the engine runs?

The heating function activates through your vehicle's climate control system — refer to your owner's manual for activation steps. It's not a standalone switch.