how early does terracotta museum open and how far is it from the train station?

The opening hours is 08:30 to 17:00 (March 16-Nov.15), stop check-in at 18:35; 08:30 to 16:30 (Nov.16-March 15), stop check-in at 18:05.

It is about 22 miles from the Xian railway station to the museum. At the east square, there is tourist bus line 5 (or bus no. 914 or 915) to the museum directly.