Hi ! my question is related on journey by train from Shijiazhuang to lhasa n from there to kathmandu , nepal.

Hi. ! i am a Nepalese citizen, currently in Shijiazhuang, China, for my study. I want to go back to Kathmandu for a vacation through land. I need to know tht if i can take a train to lhasa n then to kathmandu by vehicle. Do i need to get travel permit for Tibet, if yes, how can i get one ? and can the permit remains open when i come back through same route ?