On reading through the intro 1st level encounters and side quests in chapter 6 I decided to have my established 3rd level party start right from that point and not from the 3rd level point.
I purchased and printed out the players copies of red larch and the valley region. Being PDF's I printed them using the poster method at 150% and 160% so after a bit of cutting and taping some decent mini poster maps provided excellent reference.
Traveling to Red Larch while trying to follow the trail of some brigands the party explored and learned a bit about the town and ran through most of the 1st level encounters which I found VERY well setup and actually drove the party to needed extended rests a few times. Good intro the troubles of the reason and a good amount of coin in their purses for the first time made them quite interested in exploring the troubles of the region. Lot of play time with lower XP and higher gold was different from our normal sessions but actually quite fun.
The offerings of Red Larch as a town were quite an interesting balance. Party was thrown off by needing to deal in used weapons mainly as there is no real weapon / armor smithy in town and the provided npc who deals in used merchandise was very fun to play out.
I am avoiding talking about encounter specifics for now so there is no spoilers out there too early.
in the end a 7 hour play session had them go through 3 of the 1st level areas plus explore town and meet a lot of npc plus start some investigations into the nature of the area and the first few hexes out from red larch.