I have spent much time in China and have an idea about the trains there.
Buying a ticket at a ticket office shouldn't be a problem as most of them speak english to a degree. They are located all around and the signs are also in english. I take it your flying into Beijing? There should be a ticket office at the airport. There are a few types of seats you can buy, hard, soft and sleeping depending on the length of the trip. DONT buy hard as it's very uncomfortable and crowded and the prices are very cheap. Ask your travel agent for help on prebooking a seat and timetabes. Also i would recomend a telephone card for your travels there as its a bit difficult to call around and expensive to call outside of China. Tried a few that weren't that great but found that at 2 steps connect.com has one of the best rates and connections. Well hope this helps and have a great trip, it's a fantastic place to visit.

