Do I need both left and right end caps, or just one?

This is a single end cap—either driver or passenger side. Order two if you're replacing both sides of your rear bumper. Check your current setup to see which side needs replacement.

Will this bolt straight to my factory bumper beam?

Yes. This cap uses the same factory mounting points as the original, so it bolts in without drilling or fabrication. Torque bolts according to your vehicle's service manual.

Does the chrome finish come ready to install, or do I need to prep it?

The cap ships ready to bolt on. Inspect the finish before installation and wipe clean with a soft cloth if needed.