Do these need any wiring work?

No. The bulbs are already in place and you're connecting to factory harnesses — just plug them into your existing side marker sockets and you're done.

Will these fit flush with my bumper or do they sit proud?

They mount at the factory fender points and sit flush like the originals. No gaps, no adjustments needed.

Can I reuse the bulbs if I want to swap lenses later?

Yes. The bulbs are standard replacements — if you ever pull these off, the bulbs come with you and work in any compatible marker housing.