This mission introduces fire fighting and the concept of the Carter's Post.
Since the wood from the last mission carries over to this one, you will have enough wood to start with. Build two hovels and immediately build about 8 wells through out the estate near all the buildings as soon periodic fires will break out. There is a small open space in the stone pile, which is just big enough to fit in a well. That helps securing the quarries, which are built next. Build two of those on either side of the well and place four Ox Tethers. Build a carters post and as soon as you have more that 20 stone (two ox-loads) in your stock pile send them in batches of 20 to the neighbouring estate. Once the rebuilt keep is 98% completed, all your buildings will go up in flames. That's a scripted event and cannot be prevented. The well workers will actually manage to extinguish several fires, but they will be forcibly removed for the next mission.
Alternative Approach Edit
As always you can plan ahead for coming missions. As you have been given control of the Harbury estate, you can build on it, but the wood has to come from the stockpile of Slaughterford (your home estate). Since you've been chopping wood by the truck loads since mission 1, you have more than enough of it.The key is to get rid of the two packs of wolves which lie in ambush on the neighbouring estate. These animals are more dangerous than one might think. The only non-military units, who can kill them are hunters and their dogs. Build two hovels, but wait until the new peasants arrive at the campfire. Then surround each pack with 5 hunters posts. They'll first start to kill the hunting dogs and will then attack the arriving hunters. Many a dog and hunter will be killed, but so it happens to the beasts. After about 5-10 minutes of massacre all wolves should be gone and the hunters start doing their jobs. That has the added bonus of starting the next mission with a richly filled granary.
You may also wish to build 10 to 20 saw-pits on the beach next to your home estate. That little forrest on the beach takes up space that will be needed in later missions. To prevent the stockpile in Harbury from bursting, delete the hovel next to it (rebuild somewhere else) and place a second stockpile next to it.
The final step for preparation is to place some wells in strategic places (the spontaneous fires will continue in the next mission) and to get rid of 4 rather annoying trees. Two of them are right across from the keep and two are near the granary. Place two sawpits next to each group. By the time the scenario is finished, they should be gone.
If you want to gain more time to "prepare" the Harbury estate, do not start to ship stone to it before half the time is elapsed. Ship the stone in batches of 50.