A head gasket doesn't usually cause it to quit running unless they suck a lot of water and push a piston out the side.

Check the underside of the valve cover or oil cap as George suggest, it will be nasty if you have water in the oil. Also the oil in the pan will be milky. Pull the drain plug and let out just a small cup of oil, if its got water in there, it will come out first.

While you are checking, look at the PCV valve, it might be bad. Sounds like you lost more oil? PCV valve go bad and suck oil into the intakes which will cause smoke out the tail pipe.

Joe