The cylinder will probably need to be rebored in any case. If the crankshaft is removed and the rod hanging free, use a 2x4 or similar on top of the piston and nudge it loose with a hammer, stopping before the piston hits the bottom, then tap it back out the top. The piston ring grooves will likely be damaged as well, but since the cylinder will need to be rebored you'll need new pistons anyway.
