Do these markers plug directly into the factory harness, or do I need an adapter?

Factory harness compatibility is not confirmed — test-fit the connectors before committing to installation. You may need an adapter depending on your wiring setup.

Will these fit if I already have a custom front bumper or lower valance installed?

These mount at factory side marker locations on the stock bumper. If your aftermarket bumper or valance uses the same mounting points, they'll work. If not, you may need to drill new holes or use adhesive — measure twice before you start.

Can I paint these before installation, or should I install first?

Install first. The smoked lens finish is permanent — painting could damage it or affect light transmission. Once mounted, you can accent the surrounding bumper area as needed.