Nissan Repair: 2000 nissan sunny gq16 timing, blown head gasket, coolant system

Question
I have a Nissan sunny 2000 model that mixed water with oil and I still drove it for more than 150km, now the engine has a sludge, cream in colour and thick... Can you help me with what needs to be replaced in the engine, how to clean it up thorough & using what... and the timing marks too...

Answer
sorry for delay but was away on holiday the cause of this is a blown head gasket the only real cure is to remove the head gasket and to get the head skimmed and then replace using a new headgasket and bolts to tighten the whole lot down and you will also need to flush the coolant system and the oil system so around a month time drain the oil and replace the filter then fill up with oil again