Remove the duck & Armagnac sausage from its casing and place in a large skillet over medium-high heat. Brown the sausage, breaking up any large chunks as it cooks. Using a slotted spoon, remove to a large bowl and set aside. Pour off all but about 2 tablespoons of the sausage fat from the pan. Place the pan over medium heat. Add celery, carrot, shallot, and leek. Cook, scraping up the crispy browned bits from the bottom of the pan, until softened and translucent. Stir in dried and fresh pear, cook one minute more. Add veggie mixture to the reserved sausage.
While the sausage/veggie mixture is still warm, stir in the herbs. Add the toasted brioche, mix to combine. Season with salt & pepper. Add melted butter, eggs, and stock. Using your hands, turn the mixture to combine, making sure all of the bread cubes are moistened. Add additional stock, if needed.
For stuffing: Loosely fill neck and main cavities of turkey with stuffing. Generously butter baking dish. Spoon remaining stuffing into prepared dish. Cover with foil and bake alongside turkey until heated through, about 25 minutes. Remove foil. Bake until top of stuffing is slightly crisp and golden, about 15 minutes longer.
For dressing: Preheat oven to 350 degrees F. Generously butter a large baking dish or casserole. Transfer stuffing to prepared dish. Cover with foil and bake until heated through, about 40 minutes. Uncover and bake until top is slightly crisp and golden, about 20 minutes longer.
Preheat oven to 325 degrees F. Spread brioche cubes on rimmed baking sheets and toast in the oven until golden and slightly crisp, about 10 minutes. (Be mindful not to let the brioche burn.) Remove from oven and set aside.