Can I spend overnight in Chengdu Shuangliu Airport?

I am arriving CD Airport about 02.00 am. and in the early morning I will go to buy ticket to Jiuzhaigou at Chadanzi bus station.
My question is
1) Can I spend overnight in CD Airport about 3 hours?
2) Is it possible to get the ticket to Jiuzhaigou without advance booking?
3) Which bus station between Chadanzi and Xinnanmen have more chance for me to get the ticket?
Thanks for your suggestion.