The above advice is basically sound. I would recommend that you do remove the plug then turn the engine over by hand. When you get the piston stuck or at TDC, move it gently back and forth and see if you feel any slop. If it is tight, with no play, then I would recommend that you start the engine and run it for the full tank alternating from max RPM to super rich and gurgling just using the mixture screw. You may want to do this twice but after the second time, set the engine to max rpm then back off 300 rpm by making the engine rich then fly the plane!