1 and 2 aren't a problem with this game.
1) I've only a shit Radeon 9200 (gig of RAM, Athlon 2200+) and it runs fine (anywhere from 17-60 fps, with it averaging at around in the middle) in 960x720 or whatever...everything maxed. If I take the settings down a little, it very, very rarely drops below 30 at that resolution.
2) I don't have oodles of time to play an MMO, but WoW is pretty nice about it where you can earn experience multiplier based on how much time rested at an inn or logged off. You tend to level quickly and really don't fall behind a lot if you only play 5-7 hours every few days or so. Picking a PvE/Normal server is good if you don't want to worry about getting beat down. I play on a PvP server and just stay out of the contested zones...that way, I can play PvE to build up and then later tackle raids and defenses, with a little straight-up dueling in there for good measure.
WoW feels more like Diablo II than it does most MMOs I've tried. I've never really gotten into any of them until now. Pretty, compelling, and fun.