Cummins KTA 600 - Leaking oil under cylinder head?

Have an old Cummins KTA 600 which appears to have a major oil leak from under # 3 cylinder head. How involved would it be for me to fix this myself?

The engine sounds good otherwise. I dont know the history , but i am only going to be using it from time to time as a backup truck. Id like to try and stop this leak before i drive it too far and test the rest of the motor out on the highway.

Any advice on these old motors would be much appreciated. Cheers

 

The leak is on the turbo side / your passenger side. Yep , being individual heads I was hoping it could be pulled fairly easily. I'm a mechanic by trade here in Australia never opened up any big cummins motors. I should be able to get my head around it. Anything I should be looking out for?

 

Posted a photo above. After half hour idling the oils dripping on the ground!! Doesn't seem to be rocker covers. Almost certain it's leaking from under the heads.

 

Photo posted. Any ideas man?