Buying my first telescope..............Need help!!?

My son is 13 years old and he has been interested in science since he was young. We have both went to our local observatory which got us even more interested. We have been looking at telescopes and we found a great review here http://findascope.com/. So, we chose to get the Orion SkyQuest XT8 Clic Dobsonian Telescope at Amazon. We don't know much about which scopes we should get, about collimating, and all the extra add ons. Also, please give lots of information and if I should get a different telescope By the way, we want a telescope to see planets, stars and galaxies if possible. I really need all the advice I can get and tips for a beginner. Thank you for helping.