I wouldnt replace the engine, sounds like she's ready for a new piston, and sleeve. You will have to break in the engine again after installing, here is the link to towerhobbies replacement parts for the OS32, its like $59.00 for new piston , and sleeve. Daz...
http://www2.towerhobbies.com/cgi-bin...pgm?I=OSMG1940