Hi, you dont need to take the head off to check the rockers, just the cam carrier.
The injectors do need to come out to do it and then its all the I think 13mm bolts, make up a template out of card as the bolts are different lenghts and undo them gradually and it should start to lift from the pressure of any valves that are still open.
Remember to find and account for all of the needle rollers that will of come out of the rockers that are broken, I think there is 15 in each one.
You should also check that the cams havnt moved on the gears by making sure that both timing pins will go in properly.
Once it is all off it is worth putting a straight edge across the valves, any that are sitting low will be bent and need further investigation, its quite rare but worth checking when its all apart