Xian/ Lhasa trip

My husband and I will be arriving xian at 1130 pm on tiger airline from Singapore on 9 th sept. We will be staying 9 th and 10 th night in xian and fly to Lhasa on 11 th sept , 2 nights in Lhasa and back to xian for 1 night ,13 th sept . We hv to fly back from xian on the 745 am flight on 14 th sept. Would appreciate your planning itinerary for xian and internal flights . Kindly advise of itinerary , visa and costing of trip. Accomodation will be on our own. Thank you. We are Singapore citizens.