You better have a really good reason to do something like that. Basically, you pull the engine, remove the cylinder heads, remove the flywheel, remove the magneto, remove the water pump/magneto housing, and split the block. If you are going this far into the engine, which is all the way, you might as well change out the seal at the other end of the crank, which is in the water pump/magneto housing, change the 2 outer crank bearings on each end of the crankshaft, change the piston rings, and change the outer piston rod bearing. You could also clean up the cylinders by using one of the triple spinning honing tools, and clean up the pistons with a 3M fiberglass drill wheel or just replace them. You don't really need the service manual to do all of this. The only tricky thing is removing and replacing the crank bearings. Which is to just heat up the inner bearing ring with a propane torch briefly, and slide it off before it cools. You will also need new cylinder base gaskets, new high temperature Polaris O-rings on top of the cylinders and some motorcycle engine block gasket maker for putting the two cylinder block halves back together. Also, all of the other bearings and seals mentioned above.