Travel in Ngari is still not what you'd call easy or comfortable, but improved roads, new bridges and telephone lines have made it more physicially accessible. If you want to make a trip to Ngari, As a foreigner you should have those permits: An Alien Travel Permit, a military permit, a Tibet Tourism Bureau permit and a foreign affairs permit. And the best way to do is that you arrange a Land Cruiser trip in Lhasa the travel agency will organise all these permits for you.