Do I need to remove the existing fog light housings to install these?

No. These bezels bolt over your factory fog lights using the existing mounting points — you're replacing the trim ring and lens cover, not the whole housing. It's a bolt-on job.

Will I need new bulbs, or do these work with what I already have?

Your current bulbs stay in place. These are bezels and lens covers only, so your existing fog light bulbs continue to work as-is.

Can I paint these, or do they need to stay chrome?

They ship chrome and clear. Painting is possible if you want to match body color, but that requires prep and clear coat — plan for disassembly and a paint shop if you go that route. Out of the box, they're ready to bolt on as-received.