I'd use a cometic r/c gasket, with as said sealing by the half moons.
When you use a cometic gasket fit in position, then trim the ends as needed, some can be a bit long where the ends are by the cam bearing housings, just need a slight trim sometimes.
As said bearings very easy to do, I wouldn't bother unless they are noisy, but I would replace cam seals with viton ones if not already, they're vastly better and around £9 each.
tabetha