Maybe a bit late to reply..

I use to heat the crank case on the electric stove on low heat and use a piece of brass tubing and a small hammer to knock out the bearing.

Before I put the new bearing in, I cool it down in the freezer for a hour or so. Then I heat the crank case again, I swiftly pick up the bearing from the freezer, using a glove (so my fingers won't heat it up again), then I insert it into the crank case. So far, I have always managed to do this with finger pressure only.

If the bearing has a dust-protection plate at one side, then make shure you don't put it in upside-down.

Some people just ram it in (no pre-heating), using a wrench socket and a hammer but that is too brutal in my oppinion. This might damage the bearing and/or crank case.

Check carefully that the bearing is inserted all the way down to the bottom of the seat.

Check that the crank shaft turns freely with no binds.

I use to mount a propeller, flip it over and listen to the bearings before i assemble the engine further.