trains from Beijing to Hong kong, Feb 2012

Hi, My daughter and I are flying to Beijing after staying in Hong Kong.
I have two questions:
1) We will fly in on Feb 12 (Sunday) and are flying out of Hong Kong on Feb 15th (Wed)
We would like to travel by train from Beijing to Hong kong. Does anyone know when the trains are going that way? (preferably a private sleeper)(odd or even days???), I can only find a 2011 schedule. When can we buy tickets - can we do that in Hong Kong before we fly to Shanghai and Beijing? Being just after the Chinese New Year, is it going to be very busy and will the usual tourist sites be open?

2) Do we need to get a Chinese visa prior to flying to Hong Kong (In Australia) or can we do that in Hong Kong? (for entry to Shanghai and Beijing. To travel to these two places, is it a single entry visa?)
Thank you