I think I'm having a similar problem as you. Mine won't go into any gear with the car running and I didn't want to force it into gear, but if I start the car with it in gear and the clutch pressed in, it will try to take off. My fluid level is fine as well. It is dark, not quite as dark as yours, but it's noticable. I think I'm going to try the slave cylinder first.

I just pray to God it's not the clutch. I would think if it was the clutch, that instead of just all of sudden it quits working, it would slip first and eventually it just wouldn't have any material left on the disc. Also, I think if it were the throw out bearing, you would hear a lot of clanging around and I don't think it would go into gear or at anytime.

-Roman