Name/Train no. of Express Train from Haikou Meilan Airport to Sanya

We need to catch an express train from Haikou Meilan Airport to Sanya Tianfuyuan Hotel. Please advise if we can purchase the train tickets in advance or only on the day we arrive at the airport in mid January 2012. Which station should we alight in Sanya, how much is the train tickets and how long is the journey from Haikou Meilan Airport to Sanya? Thank you.