Hi Greg,
You can strip down the engine and put it in a large vise with a peice of wood behind the case. If it is a long shaft, you will need a big vise. You may have to cut a hole in the wood to allow the shaft to come all the way out. This is hard on the cheap bearings. Get some new high quality bearings when you are ready to reassemble it. It is easier to trim the case with intregal shroud. Just use the old case as is with the new cylinder and see how it runs. It is a wast of time pulling the shaft unless you are going to use good bearings from your local bearing house. I'm sure that the metro-plex has some great deals on bearings, just take the old ones to them for a match. Remember that there is a seal at the front of the shaft to maintain base compression.

Dave