This is actually very easy to do. Dissassemble the motor so that only the block is left. Grab a pair of channel lock pliers and grasp the bottom of the block around the area of the carburetor. If you have a gas stove at home this becomes even easier. Turn on the burner and heat the block very gradually and slowly. Once you begin to see just a wisp of smoke come out of the block(the oil and water burning off from inside the block) tap the block on the counter top lightly. The bearing should just fall out. The trick is to heat the block just enough so that the bearing just falls out. When heating the block try and keep the flame away from inside the block and heating directly on the front bearing.

To reinstall the new bearing, place the bearing on the crankshaft as it would go inside then engine. Reheat the block as before and slide the crank and bearing assembly into the motor. This is abit of a juggling act, but putting the bearing in as an assembly helps to line it up easily with the front bearing.