We will take G train from Xian to Luoyang/Longmen to see Longmen Caves and then want to continue to Suzhou (near Shanghai). We are thinking to take the G train from Luoyang/Longmen to Zhengzhou and then overnight train from Zhengzhou to Suzhou. Is the station the same where the Luoyang/Longmen train arrives and the Suzhou train departs? Can we buy the ticket for the overnight train at any station other than Zhengzhou?