How should i plan for my trip from Changchun to Changbai Mountain?

You may take a bullet train to Dunhua from the Main Railway Station. The trains are available from 05:47 to 21:01, and the trip takes about 1.5 hours. A second class seat costs CNY 80.5; a first class seat costs CNY 97. Then, take a bus to Erdaobaihe (about 2.5 hours). Upon arrival, you can find the hotel. You can take a taxi to the mountain from the hotel for about CNY 30. Have a good day! :)