I had the missfortune to see my Hobbico SU-31 break apart in mid air the other day. Wings came off and the rest went in like a high speed yard dart . I thought I was going to have to go get a shovel to get the engine out of the ground. It broke the block where the muffler bolts on taking some fins with it. I tore it down and cleaned it up, but the question is it's a Tower 75 and is it worth fixing. A new casting is about $35.00. If so how do you get the seleve out and how do you remove the crankshaft?