WoW is probably one of the easiest MMOs to get in to. It's pretty straight forward. The character creation screen should have a description of the classes. It's been over three years since I last played, but it was the first MMO I ever played and I picked it up really quickly. If I can do it, surely you can.
Just go from yellow exclamation point to yellow exclamation point to get quests. They usually form a nice chain for you and lead you to the next area when appropriate. You'll get the option to dungeons when the time is right and those will give you some better loot. Lore is kind of hinted at in quest text, so read that if you want that information. Combat, well you just read your abilities and use them in the most effective way for the situation. You'll figure it out. If you have any specific questions, ask them.
If you think WoW is impenetrable you will have a very rude awakening trying other MMOs.