If it was me, I'd pull the head and have a look. You're not going to be able to stick a camera in the glow plug hole and see the piston or valves, all you can see is the combustion chamber.

Best case sceanrio is new valves/guides/seals, and the head needs to come off for that. Worse case is burned piston/broken pistons, and the head has to come off for that, too.