Do I need new bolts to install this gasket?

Reuse your factory header bolts if they're in good shape — just clean the threads and apply a light coat of anti-seize compound before reinstalling. Tighten in a cross pattern to ensure even clamping pressure.

What prep is needed before I bolt the header back on?

Clean both the header flange and cylinder head surface with a gasket scraper or wire brush to remove any old gasket material or carbon buildup. A clean, flat surface is the only prep this gasket needs.

Will this gasket seal a warped header?

If your header flange is warped, no gasket will seal it reliably. Check the header surface with a straightedge before installing — if it rocks, the header needs to be straightened or replaced first.