Ulaanbator->Beijing Ticket Inquiry

Hi there,My name is Belveen, from Malaysia. I Have some queries regarding the train service from Ulaanbator to Beijing. How much are the tickets? How do i make the payments for them ? When does it leave (the schedule).. I will be going to Ulaanbator from Beijing via train, so i will arrange a visa for entry into Mongolia, however if i go back to Beijing will i need to get a visa?Hope to hear from you soon. Thank You.