There's some useful stuff in the DMG, but the parts about ideals, and flaws and whatnot won't work for me - I dislike that whole mechanic, although I can (and probably will) replace it with a couple of other things. I'm working on stuff related more to handling whispers, gossip, rumors, reputation and the like to compliment more direct social interaction (although I still don't have a system I'm 100% happy with for the former).I recommend taking a look at the social interaction rules in the DMG. It provides a useful structure for creating a challenge as opposed to just social interaction for the sake of exposition. An "intrigue heavy social interaction kind of thing" is going to lack a lot of exciting stakes, unlike combat, so that's another thing I'd look at and the challenge structure in the DMG will help.
Stakes won't be an issue. Combat will still be a significant part of the campaign, but it'll be more like duels, knives in the dark and chases though alleyways rather than rooms full or Orcs. Stir in some high stakes mission impossible style infiltration and political shenanigans with deadly consequence and I feel like I'll be ok if I design it right. My best weapon to create a sense of urgency there is time, which is actually just as true in a dungeon adventure for the most part.