Will these lights work with my wiring harness, or do I need an adapter?

These are direct replacements for factory turn signal housings. Your existing wiring plugs straight in — no harness modification needed.

Can I use these with a custom bumper, or do they only fit the OEM setup?

They mount at factory bumper points, so they'll fit any bumper that uses the same mounting location. If you're running an aftermarket bumper, confirm the mounting holes align before purchase.

How do I handle bulb replacement if one burns out?

Access is the same as factory lights — remove the housing from the bumper and swap the bulb cartridge. Bulbs are not included; replacements are standard automotive turn signal bulbs available at any parts store.