If you are traveling on official gov't orders, the easiest way to get to the base is on the CFAY Narita Shuttle. Here is the link where you can sign up:

http://www.cfay.navy.mil/Narita_Bus/...0Web_home.html

It departs from T1 only (near N2 exit) and will drop you off in front of the PSD Office on the base. To get to the New Yokosuka, you will have to go back off base though. It's about a 7-8 minute walk, or you can arrange to have the hotel pick you up from PSD.

-suppo