Zen linked to the description so I won't repeat that here. But, as to your other questions...

Required skills would involve riding in a tight pack, and cornering at high speeds while staying in that tight pack. I'm not sure what your experience/comfort level is in those areas, but I think a good approach might be to go attend the first of the weekly races as a spectator rather than an entrant. Station yourself by a corner and watch one, and you'll get a good sense of whether you're ready to dive in now or whether you'd want to get more skills practice in first.

There's no one answer to how fast someone can take a turn. Depends on the angle of the turn, the camber and condition of the road, the arc radius/path you are able to take thru the turn (sometiems you can pick, but in a criterium you'll have people around you so you might not be able to take the optimal path), road conditions, how good your tires are, etc. It's definitely a good idea to pre-ride the course so that you would be familiar with the turns and know when you can speed through them and when you might need to lay off a bit.