It takes about 15 hours. Best would be to leave around 6-7pm and reaching Beijing at 10 in the morning. The other way should apply also. The price was 317RMB in 2001. That's one way, and for the hard bed and middle bunk (there are 3 layers of beds, lower most expensive, if I remember well). ITs not that bad lah hard bed, just that the mattress is 4-5in thick instead of a super plush mattress in first class. THat's what I was told, I never been on the first class before, but I think its over kill.
If you go for the hard bed, take the middle. That's becuase the lowest one is the most expensive and you get a lot of Chinese people hanging around your bed. The top most one is the cheapest, but it takes a little effort to climb up, and although its a non-smoking train, people still smoke and when they do, you dont want to be on the top most bunk.
Hope that helps.