Hey man
the plugs you rever to is the exhaust manifold studs, it is a common thing that they snap of and needs to be replaced. if it is not replaced the exhaust gasses might start leaking from there which if it leaks excessive could cause your turbo to loose boost. it is a fairly big job to remove and replace the broken exhaust manifold studs as you need to remove the turbo, dump pipe, water lines, oil feed and return lines. drill and remove broken piece from cyl head and fit all new studs and gasgets. you can use a straight edge to see if manifold is warped, if it is straight no need to skim. probably a days job if all goes well.
hope this helps