Not too hard but a couple of pointers:
Do the cambelt & waterpump too- it's only £30 extra
Repace both cam oil seals (dizzy end too), the camshaft bearing stud/nuts are M7 and require carefull torquing in the correct sequence, you risk either stripping the stud out the head, or breaking them cam if not.
Haynes has the proper sequence to set the piston position, have you got a vernier pulley to fit too?
Plently of oil over the cam/tappets on installation too, if the tappets have been sitting a while, then leave them in oil for abit bucket side up.
Hope this helps,
Pete