This is what I've been dealing with this weekend:
The remains of the stud wound out easily once I'd got a hole in it that would take an Eze-Out. Cutting the hole took 3 hours with a tungsten cutter though, partly because access was er, 'limited', to say the least but mainly because no drill bit I had - even brand new left hand bits - wouldn't touch it, dunno for certain what these studs are made of but the new one has A2 stamped on the end so I assume that it's stainless.
Problem I've got now is that coupled with the lack of access, the metal pipe just below the red oval is dead in line with the axis of the stud so fitting the new one is a challenge.
And the oil on the side of the head? Every rocker cover bolt on the right cover was slightly loose (and so were a few on the left), needing about a quarter turn to reach 9Nm, I'm guessing it's in need of new gaskets.