How to replace?
A heater gun and a freezer comes very handy in this process. The centre of the wheel is mostly made of aluminium while the bearing is steel. The difference in the thermal expansion makes the process easier and you can avoid damaging the wheel.
Warm up the wheel centre with the heater gun, remove the old bearings and the spacer.
Clean and re-grease the wheel hub, remove the new set from the freezer and if required grease it. Fit the new bearings and the old spacer.
Expert advice: The heat difference might allow you to fit the new bearing without any tools, however if you need to, you can use the old wheel bearing to drive the new one into it's place. This will prevent damaging the new bearing.