Which I did not say. Storm lay off and chill.
1) As LD said, while ALO has magic, that's the second game in the series. SAO (the first game) does not.
2) You may, but remember that the character itself is a real life person, and only their in-game character can be modified as such. Plus the skin is eventually forced to look like their real life self, so it's up to you if your character is role playing too.
3) No. There are no engineering classes in SAO, and no real machines or anything similar. Stick to warriors, because that's what the game is.