When you put the four gaskets around the spark plug holes back in consider using a gasket sealer like Permatix Hi-Tack to hold them up against the cylinder head cover.
Worst case will be if one has dropped into the camshaft chain housing. It will require patience and a retractable claw hook to fish it out, along with mirrors to see what you're doing. Don't ask me how I know.
If you're lucky the gaskets will be sitting atop the camshaft and hopefully still intact. If there's any doubt as to condition replace them all.