Exhaust Manifold Gasket Replacement

[Ian Sinclair]

There's a ticking noise coming from my 99 2.5 Boxster. You can't hear the ticking whilst idling or when the Windows and roof are closed. But when the window is down it bounces back and can be heard on acceleration up to about 40 mph.
I believe it could be the exhaust manifold gasket leaking ???. My question is how easy is it to remove the exhaust manifold to replace the manifold ??? Your thoughts would be appreciated guys ??