You may be able to do it yourself without a press. I've done a few single cylinder engines this way. Block up the crankcase so there is room for the crankshaft to come out. Use wood or other material to avoid damaging the crankcase mating surface. Use a hammer on the end of the crankshaft with a wood or aluminum block to prevent damage to the threads to drive the crankshaft out. For further protection of the crank threads, put the nut on it till it is almost flush before using the hammer and block. If it doesn't move with reasonable blows, heat the crankcase around the bearing area with a propane torch until any oil begins to smoke a little (around 450 deg.). The heat may damage the seal, but it probably needs replacing anyway. You'll need to heat the crankcase to get the new bearing in according to the service manual. Probably not as hot, though, as there won't be rust and varnish on the parts.
Steve is right, though. A shop press is preferred and makes quick work of it.
