well, if you've got 15 bucks to spare, why not just tell him that you'll give it another try and see how it goes. You can always just cancel your subscription after the month is over if at the end you find you don't feel up to getting back into the game
And I'm no Wow player, but I've know folks who are... and from my knowledge, that particular expansion was a good while ago... so there's probably gonna be some stuff to catch up on lore wise (and probably mechanic wise too.)
