Well your class/race combo is not a big deal in wow. Stats change depending on your gear, and the only thing races really give you is racials, but none of them will make a huge difference.
You can find all the racials here
http://www.worldofwarcraft.com/info/races/
Again they don't make a big difference, so just play a race you like.And like the guy above me said, you can obtain every skill available to your class by buying them so you cant mess that up.
You use talents (unlocked at lvl 10) to specialize into specific roles. And you can redo your talents at any time for a price.These are pretty hard to mess up while your leveling,just don't waste them. When you get to lvl 80 then the specific talents you choose will become important since you will want to maximize your dps/healing/tanking abilities.
WoW isn't like a lot of korean mmorpg's where you can mess up your character forever. There really isn't anything you can do to mess up your character forever. If you told us what class and role your interested in, we could suggest a talent tree for you to go down, and tell you what type of gear to try to collect.