3 weeks is really the minimum amount of time that I recommend for a north to south trip in Vietnam. Traveling here is pretty easy, but you should prepare for it by doing extensive research. I've been to VN 7 times. and am also coming to Hanoi again in March. I recommend domestic air travel since trains are still on the crude side, and none too clean. Road travel should be avoided as much as possible.

The 3* hotels here are wonderful. I've booked myself at the Hanoi 3B Homestay in Hanoi for a $29. suite during their sale, but prices there are still very low - great reviews! You can travel entirely on your own or use the services of a good local agent - I recommend my wonderful agent in Hanoi, Mr. Diep Tran of Vietnam Tour LTD - a very responsible and generous travel agent.