A Human Freemage (who I believe is the only one who can learn Dark Magic--I'll have to confirm/deny this and get back to you--) can also learn Light Magic.
All the races are limited in what they can learn, which of course is also limited by what type of character they are. All characters can be three things: a fighter of one type or another, a magic-user, or a secondary fighter to play back-up with the main fighter. (Of course you can play all fighters or all mages, with lots of potions!)
So far I've played through the game several times, usually with vastly different team make-ups. And just because your character can use a skill does not mean that he/she (gender has no bearing) can master or grandmaster it. Even though the game is very, very linear (like most of the M&M's) it can be wildly different every time. No single party can ever grandmaster every skill in their repertoire, much less every skill in the game.
Yes, the game is still buggy. Most of the old bugs have been corrected, but a few new ones have surfaced. Most have fairly easy work-arounds. (I ran across one in which my main fighter, an Orc Barbarian, could not use his main weapon. I left the game in disgust, only to find that he was back to normal when I reloaded. The puzzles are tough, but there are clues to all of them.
I think the game is specifically designed for replay, what with all the combinations/permutations of character creation.
And Ossie, I still haven't gotten anywhere near being able to go to that Elven forest just yet. But I'm working on it.