Well bro I'm not sure what kinda car you drive and mods. I for one know all about blowing head gaskets, seems to me I go threw them like candy. Anywho, check your radiator (when its cooled off!) and check for what they call milkshaking, when oil and coolant mixes they tend to make a milkshake kinda of mixture. As for trouble shooting should be easy if you are an n/a motor. But turbos with coolant and oil lines going threw the turbo could be this cause because a seal might go bad. Good luck bro, sorry I can't help I just started tuning cars the last 2 times I had the car dealership do it they seem to last only a few days. Anyways you'll need a headgasket new head studs (most likely) new coolant, coolant flush, oil and new oil filter. Also I wouldn't drive the car if you think its a blow head gasket. Chances are you will only end up doing more damage than good, also you risk warping the head.. I wouldn't drive it bro.