If it is the headgasket.............

Headgasket, best replacing with at least a group A one
Headbolts
Camcover gasket and 1/2moon seal
Oil/filter
Belt if it needs replacing and poss adjuster pulley if needed

Head might poss need a skim, its worth getting checked.

Also ur sig says coming soon stage 3, how many miles as it done?! if a few then to be honest you wanna get compression tests done b4 to see how rings etc are plus general health of all the engine seals etc. Also things like valve stem seals might be worth doing while the heads off cos their a pain to do with the head on!!

Nothing worse than doin just the headgasket to find out later other bits need doin, costs more but in long run doin it once works out cheaper