Do I need hardware to install this?

The gasket itself has no fasteners. You'll be reusing your existing header bolts and studs—just unbolt the header, swap the old gasket for this one, and torque back down to spec per your service manual.

Should I prep or clean the mounting surfaces before installation?

Yes. Scrape away any old gasket material and carbon buildup from both the header flange and cylinder head surface with a gasket scraper or wire brush. A clean, flat surface ensures a proper seal and prevents leaks.

Will this stop an exhaust leak at the header?

If your leak is at the header-to-head interface, this gasket will seal it—provided the header and head surfaces are flat and clean. If the leak is elsewhere (manifold cracks, loose bolts elsewhere in the system), you'll need to address that separately.