[IHCub1450]

Yesterday I was using my Cub Cadet 1450 to mow the backyard. The tractor mowed and ran fine, up until when I put it back in the barn. The tractor had been sitting in front of the door from about 12:30pm-9:30pm. Since it was dark out I had not noticed that the oil drain plug had fallen out, consequently, allowing all of the oil in the crankcase to drain out.
I did not bother to check the oil when I put it away, as I had checked before I started the first time, as I always do. Anyway, I started the tractor, it didn't start very well and made sort of a clunk-clunk-clunk sound. I knew the engine sounded not quite right, but since I was only putting 20' feet into the barn, I figured I would have a look at it inside, as it was dark out and I couldn't see anything, anyway. It started blowing blue smoke from the front of the machine. At first I thought it was probably the deck belt or something like that. Upon putting the tractor back into the barn, I pulled the dipstick and realized where the real problem was.
Today, I refilled the crankcase with fresh oil, that was going to drain out, that way I would be able to tell if there were metal shards in the engine.
Not being able to turn the engine over, I suspected a dead battery, I put the volt meter on it, this was not the case. I then tried to turn the the camshaft with my hands, no dice.

Not wanting to ruinthe engine further I haven't tried anything else, besides some penetrating lubricant sprayed into the spark plug hole, to try to lossen the piston.

I'm not against fixing it myself, but I'm not sure what the next step sould be.
Is there something else I should try to free the piston, or do I need to start disassembling the engine, and opening it up?