Will this fit over my existing bumper, or do I need to remove the old one?

This replaces the corner cap piece only — the main bumper stays in place. You'll unbolt the worn or damaged end cap and bolt this one into the factory holes.

Does the chrome finish come pre-polished, or will I need to buff it after install?

The finish ships ready to install. Light hand polishing after mounting will bring out maximum shine if desired, but it's not required to function or look good on the truck.

What if my current bumper mounting bracket is bent or the bolt holes are stripped?

This cap bolts to the factory bracket — if that bracket is damaged, address it before installing the new cap. A bent bracket won't hold the corner piece securely or square.