Jolly Green Monster 2

I had a good look around the engine bay last night and noticed a small amount of oil have been leaking out of where the oil feeds to the cams are (I guess that is what they are). On the right hand side of the engine (when looking at it from the front of the car) where the oil is poured into has a sort of metal black box that sits on top of the block edge. There is the same on the otherside but without the oil filler. Both then have oil pipes that run off round the back of the engine.
Looks fairly easy to change the gasket?! I hope?

Should I be worried and change them asap? the leak on the left side is the worse and there are very small but clearly marks on the heat shield below where it have dripped onto it at some point.
It could have been happening for months as I have never really looked before.

Thanks

JGM