As mentioned , they have class trials now as an option when making a new character and it will let u test a class out at L 100 . So u can do that to learn some of the new abilities or try diff specs out . I would not reroll tho , stick with one of your 80 ' s . prob the druid honestly since as a hybrid u can get faster ques if u tank or heal . Best way to learn about the class is to just play it . read ur spellbook then look over ur talents . Then do quests or dungeons to get some experience and relearn mechanics . U can also watch guides on youtube or read em online . The rotations and stuff is pretty simple and easy honestly , they removed alot of fluff abilities so u really only have a couple abilities and CD ' s per spec to work with .