Do I need to remove the header to replace this gasket?

Most common practice is to unbolt the header from the manifold flange, which exposes the gasket for removal and replacement. You'll need basic hand tools and a socket set to access the mounting bolts on your specific engine bay layout.

Do I need to prep or clean the sealing surfaces before installing the new gasket?

Yes. Scrape away any remnants of the old gasket from both the header flange and manifold surface, then wipe down with a clean rag to remove carbon and debris. A clean surface ensures the new gasket seats properly and seals without gaps.

What happens if this gasket fails or leaks?

Exhaust will escape upstream of your O2 sensor, throwing a check engine light and throwing off your fuel mixture. You'll notice a hissing sound near the header area and possible rough idle. Replacing it stops the leak and restores proper exhaust flow.