Thanks William, and everyone else...

I did what Will said before i read the post (about just swapping pistons), and am pretty pleased. I took my time and cleaned everything as i went along, and the whole process went smoothly. Once reassembled i put her back in the plane, put teh electric starter on it and it fired up after 2 rotations. Starts just as good if not better than before, and the new muffler and crankcase look good and sound better. Thanks all.