Hrmmm... SWG and WoW. They're really not all that similar. In WoW you've got plenty of quests to do that will help you level up. In each area, there are tons of people who will give you a quest to complete (if your level is high enough). These people are easy to spot due to the yellow "!" above their heads. Those who have quests, but are above your level are marked with a silver "!" over their head. The quests tend to be either "Kill so many such-and-such monsters," "Bring back so many such-and-such items," "Go talk to so-and-so and deliver such-and-such item," among others. Quests will give you experience, and items or money (or both). Usually, it seems as though doing quests is the best way to level.
As far as crafting is concerned, you're apparently allowed to have 2 professions. Now, you'll have to forgive me if I don't cover this accuaretly, as I haven't done much much in the way of crafting during my time in the stress test. However, you'll be able to level up your crafting skill, and you don't have worry about losing materials while crafting, as there are no failures. You can buy schematics and recipies from a trainer of your chosen skill, recieve them in quests, or find them off certain monsters.
When you choose a class, that's the class you're going to have through out the game. However, you do get certain Talents that are fairly similar to the skill tree in Diablo. Helps customize your character a little better and thus probably won't come across too many people who are exactly like you.
Anyway, hope that helps out a little bit.