Remove the cooling head and back plate from the engine. The remove the cylinder sleeve to allow room to move the rod form the crank. Pull the piston/rod out and then there is a tiny retaining clip in the side of the piston. Pull it and push out the wrist pin and viola! Done.
This is super simplified, just be sure to carefully watch how everything comes out. The hardest part usually is the sleeve. Slip a zip tie across the exhaust port then turn the crank and allow the piston to start to push the sleeve up. The you can pull it the rest of the way out.