Do these need to wire into my factory harness?

Yes, these connect to your factory cab light wiring—they're designed as a direct replacement. Disconnect the old housings, pull out the fixture, and plug these in at the same mounting points.

Will these fit both the driver and passenger sides?

These are sold as a pair—one for each side. Both housings are identical in size and mounting style.

Do the chrome housings need any prep or sealing before install?

Not needed. The chrome finish is factory-applied and ready to mount. Just clean the mounting area on your cab before bolting down to ensure a tight fit.