Stock coolers always aren't the best, so if you overclock it you'll need to get a better cooler. Water cooling is the best, but it's way more expensive than air cooling. UPDATE: You'll be able to use the stock cooler until you overclock it.
they are ok, otherwise they would not package it with that,
Yes, the stock cooler will work, but if you ever want to overclock your cpu, you want a more powerful cooler so that you can reach higher speeds. Your processor will run faster and faster until it reaches the system maximum temperature. A stock cooler wont give you really high speeds when overclocked.