Will this header work with my stock exhaust system?

Yes — the single outlet flange bolts directly to your factory downpipe connection point. You may need an adapter or custom piping depending on your current exhaust setup, but the header itself is a direct bolt-on.

Do I need to rejet or tune my engine after installing this?

Headers alone don't require a tune for most bolt-on installs. If you're also adding intake, exhaust, or ECU modifications, then a tune becomes relevant. For the header by itself, no tuning is necessary.

Should I paint or ceramic coat this header before installation?

Stainless steel won't rust, so coating is optional and purely aesthetic. If you want heat color or a black finish, apply any high-temp coating before bolting it on — it's much easier to do off the car.