Do I need fasteners or clips to install this?

Installation hardware is not included with the assembly. You'll use your truck's existing factory fastener points — check what came out when you removed the old grille and reuse those, or pick up equivalent hardware from your local parts counter if needed.

Can I paint this before or after installation?

Paint it before you bolt it on. Easier to mask and prep when it's sitting flat on your bench. Once it's painted and dry, mount it to the truck using your factory attachment points.

Does this fit without any trimming or modification?

It's designed for direct installation at factory mounting points — no cutting or test-fitting required. Bolt it in and you're done.