Train Kunming - Lijiang

We have 4 people and travel during 5-10 Dec 15 from Kunming to Lijiang.
I'd like to book for soft sleeper seats and I have questions as follow;

1. How many days should I book the tickets in advance?
2. How can I received my ticket? At train station?
3. Is it possible to book 4 ppl in the same room? If i book very early, is it more chance? or can i know before i pay that we are in same room or not (because we all women, if we're not in the same room, we prefer hard sleeper)