Will I need to drill holes to mount this?

No. This louver uses your Mustang's factory mounting points — bolt straight to what's already there.

Does it come with mounting hardware?

Hardware is not confirmed in the product listing. Verify what fasteners you'll need before install — most factory points use standard bolts, but test-fit first to be sure.

Can I paint this, or does it need prep?

It arrives black and ready to install as-is. If you want a different color, standard automotive prep and paint will work — treat it like any other plastic exterior panel.