how do i replace my head gasket on my 1998 citreon berlingo?

what is the proceedure for replacing my head gasket on my 1998 citreon berlingo diesel. oil is present around the top of the engine block however i am concerned that the job is not as simple as on other makes due to what seems to be the exhaust manifold positioned over the top of the engine block. blue smoke from the exhaust and to much oil in the sump(that was somehow missed on the mot last week as well as other niggling little problems).