Do I need gaskets or a new manifold gasket to install this?

Yes—grab a fresh header gasket set before you unbolt the old manifold. Reusing old gaskets almost always leads to leaks. Most hardware stores stock universal gasket kits, or order one specific to your application while you're at it.

Can I drive it straight after bolting this on, or does it need to cure?

You can drive it right away. Stainless doesn't need paint or finish work. Just torque the bolts to spec per your service manual and you're good. The header will darken slightly from heat cycling—that's normal.

Will this work with my stock exhaust, or do I need a new system?

It bolts to your stock mid-pipe and muffler. No new exhaust required unless you want to upgrade downstream. This header alone will flow better than factory cast, so gains are real even without full system work.