Will this bolt directly to my exhaust manifold gasket and studs?

Yes, this header uses factory mounting points on the cylinder head. You'll need new gaskets and studs are reusable if they're not stripped — grab fresh ones to be safe.

Do I need to prime or paint this header before installation?

Stainless steel won't rust, so paint or ceramic coating is purely cosmetic. If you want it coated for looks, do it before you bolt it on — easier to handle and cure without heat cycles.

Will I need custom exhaust piping to connect this to my downstream system?

Check your outlet diameter against your current exhaust piping. If there's a mismatch, you may need an adapter or custom section — measure before ordering any secondary work.