bg

I cracked the drain plug on the oil sump and sure enough there was coolant there. So I assume the head needs to be removed ?  I have never torqued the head bolts or adjusted the valve leash. That follows my credo , If it aint broke dont ever attempt to fix it !!   However I may pay a price for that now. I have removed the valve cover and will remove the rocker assembly , exhaust manifold and anything else that gets in the way. Is it fairly normal for a head gasket to fail? I have not really stressed this engine .No rainwater has ever gone down the exhaust, the tractor is always under the shed. Oil and coolant has always been maintained properly. Back in my younger days I played around with gas engines,  mostly six bangers, and the only time I saw a head gasket  fail was due to overheating and stress on the engine. Not the case with my JM.  Anyway, when I pull the head what other signs of damage should I look for? Or should I just retorque the head, adjust the valves and try  to run it?  I will say it started missing or not firing on one of the injectors the last time I started it. Lots of  light colored smoke too.   Thanks    BG