Yes. He will need to split the case to get the conrod out. Here's what you can expect to change, probably the piston and barrel. If the piston does not have lines on it and the rings still fit tightly in the grooves, you might be able to do a rings job and hone the barrel. You will need to replace the gudgeon pin bearing and big end bearing. If the crankshaft has marks on it that will need to be replaced as well. He should also replace the crankshaft seals. You might as well put in a new oil pump and have the valves re faced. At the end, if your mechanic is good you should have a good engine. You might find it cheaper to find a similar bike with low mileage that has been in an accident. It will be a lot easier and cheaper to take out your engine and put another one in. It would take a couple of hours.