The biggest problem is removing the old bearing and pressing the new one back in. Ideally you will need a hydraulic press but not many of us have one. When I have done wheel bearings I have taken the hub / drum to a local mechanic who I know and he has pressed the new one in for a drink.
The bearings are an interference fit, that coupled with water and crud from the road makes them pretty tough to remove. The last one I tried left the shell behind stuck in the hub but the bearing rings popped out. So I still needed to get the shell pressed out.