Blown head gasket or head?

There must be something wrong, there‘s water in the number 2 & 3 cylinders. It’s a pity too because I got the engine running evenly and well. Now I think the plugs are water fouled.

Anyway I’m determined to do as much of the work as I can, but this is my first rodeo so to speak. I have had a head off before only to inspect the cylinder heads on a dead engine. Anyway I can’t remember that it was that difficult and the manual makes it look straight forward. I imagine there’s an even chance the head is cracked. Is there anything I should know before getting into this?