zhangjiajiexi West train station to Jiuzhaigou

Hi,
Hope it's ok to ask many questions ..

We are planning to take a train to zhangjiajiexi West train station and then to Jiuzhaigou, are there buses to Jiuyuan Hotel Huodiba, Goukou, Jiuzhaigou ? what would it cost ?

Also can I take Didi or taxi from station to hotel and how much would it cost apx ?

Do we need to buy the national park ticket before arrival or we can buy on the day we are visiting ?

On the way back, we would like to book a private car to take us to Huanglong National Park and wait for about 4-5 hours and than to Zhenjiangguan station to take our train to Chendu. What would be the aproximate cost to hire a private car for this purpose ?

Thank you very much in advance for your assistance.
Kind regards,
Keith