Will I need new gaskets or fasteners to install this?

Factory head bolts will work, but you should use a quality gasket set rated for your engine. Existing hardware is reusable if in good condition — inspect before assembly.

Does this header need to be painted or ceramic coated?

Stainless steel will develop heat patina over time and won't rust. Ceramic coating is optional — many run these bare for the natural stainless look, or coat them if you prefer a finished appearance.

What's the difference between this and the factory cast manifold?

The factory manifold is cast iron and restrictive. This header's tubing design improves exhaust scavenging and flow, which supports better engine breathing. Temperature management is also more consistent with stainless construction.