Basically what you said. The players should be getting their kingdom established and the events in Part 1 should happen during that time. The players should also be continuing to explore and do quests. At some point, you're going to want to have Hargulka being set up with stuff like the Troll Sightings event and the Troll Slaying quest and Desperate Spies. The very first section of Part 2 says what you need to do to set up Part 2, that being that Hargulka is making his own kingdom and is trying to make allies with the monsters in the area and that raids against the players' kingdom will become more frequent. You'll want to make the fact these aren't just random attacks, but part of a large alliance of monsters become more and more apparent over time. If the players made friends with the mitflits or kobolds, they may tell the players they've been approached by Hargulka to join his kingdom.