Will this interfere with my trunk seal or hatchback operation?

Mount location is at the spoiler level, not the trunk sealing surface, so seal interference is minimal. Test fit before final installation to confirm clearance with your specific hatch setup.

Do I need to drill holes into my spoiler to mount this?

Mounting method not specified in product data—test-fit before committing to adhesive or fasteners. Bring a socket set and adhesive options to your install so you can make the call based on what you're working with.

How does this wire into my existing brake light circuit?

Wiring harness not confirmed. You'll need to tap into your factory third brake light power source or splice into the tail light circuit—standard splicing with crimp connectors.