Oil in Exhaust, Craftsman Lawn Tractor 18 HP Kohler

My 8 year old Lawn Tractor started putting out large clouds of white/grey smoke from the exhaust and dripping oil out of the muffler. It smoked a bit at first and then shut off after about 2 minutes and then belched a lot of smoke. After pushing it back to the garage and let sit for a couple of hours a puddle of oil formed on the floor. The only apparent leak is from the muffler. I checked the spark plug and it was not fouled but seemed slightly damp and black. Now that I think about it, there was a fair amount of smoke when I first started it the last couple of times, but the oil level has never gone down until today. Maybe a head gasket? I don't really know.

 

You're probably right, head gasket.