Here I go again - need help with clutch

I took the clutch cylinder off by the counter sprocket and when I put it back on, now the bike leaked out all oil from there. There is a tear in the gasket on the bottom, could that be the leak? Could I have possibly lost the piston? Also having a hard time finding a shop manual for a 2004 200 exc. I always seem to learn the hard way. I try so hard to do my own wrenching! Thank you, Nancy :bang: