It's pretty hard, especially with the "no kill" and not even allowed to melee/knockout guards conditions.
I found the best way inside is by the train tracks on the west side of the base. If you find it, there's an opening in the fence where the tracks are supposed to be. Once past the fence, if you hug the fence from the inside and follow it north, it will lead you to the north entrance of the base with only 2 guards at the the bottom
which puts you very close to the objective compared to having to slip through the entire base from the south.
Having my ghost character interact with S
