If at all possible, approach this Outpost from the North over the mountain above it. It is very hard to do but plausible at least. Otherwise come in from the Southwest and climb up on the nearby rocks to get most of the soldiers present there. You need to contend with 4 Soldiers and 3 Heavy Soldiers. There are 2 Alarm post as well. A second option fort he stealth approach is to get into the Outpost from a tunnel found to the West of the Outpost in the Mountainside.