Will this fill the stock grille opening completely, or do I need to source a mesh insert?

This is trim molding—it frames the grille area but does not include mesh or insert. You'll reuse your existing grille insert or source a replacement separately depending on your aesthetic goal.

Can I paint this before installing it, or should I wait until it's bolted on?

Easier to paint off the car. Mask and prep the back edges, paint it separately, let it cure fully, then bolt it down. Reduces risk of overspray on adjacent bumper surfaces.

Does this require any bumper sensor modifications or do the factory holes line up?

Mounting method uses factory attachment points—sensor and washer bottle areas align as designed. No cutting or repositioning needed if your donor bumper is intact.