- Head gasket can be done with engine in place.
- Clutch can be done with engine in place
- Water-pump and cam-belts can be done with engine in place
- Oil rail can be done with engine in place.
All are a pain with engine in place.
I would replace head gasket, water pump and cam belts only.
Change the clutch when you need to at a later date.
Would not touch the oil rail!
if you insist on doing all the work at once, then maybe easier to remove engine, and do a full engine bay clean up at same time. However removing the engine looks to be a pain, but never had to do it.
Peter