You won't need to the first Guild Wars to play the expansion. They are each stand-alone games, except I guess the new one, EN, requires one of the old ones(?).

 It's not technically an MMORPG at least that's what I think about it, but if you like a more team-based game (most of the game is a lot more fun non-solo) with a lot of MMO aspects and no monthly fees, it can provide hours and hours of fun.