Do I need to buy both left and right, or can I just replace one side?

This is the left side only. You can replace just this side if only one headlight is damaged, but for even lighting output and appearance, a matched pair is the better move.

Will this require any wiring modifications or does it plug directly in?

Factory mounting points line up at the OEM rocker locations — no drilling. Confirm bulb socket orientation during test-fit before final install to ensure the connector sits flush without forcing.

What bulbs do I need to buy separately?

This assembly accepts H11 and H9 bulbs depending on your low-beam and high-beam configuration. Check your vehicle's existing bulb type and grab replacements with the same designation.