Preheat oven to 325 degrees F.
Slice the cornbread and then cut into small cubes. Slice the loaf of French bread and then tear the slices into bite-size pieces. Discard the end pieces or save for another use. You should have 8 to 9 cups each of the cornbread cubes and French bread pieces or 16 to 18 cups total, give or take. Spread the cornbread cubes on a large rimmed baking sheet, crumbling some of the cubes into smaller pieces. Add the pieces of French bread to a separate baking sheet. Bake both for 15 to 20 minutes or until lightly toasted. The cornbread will require more time in the oven then the French bread since it has more moisture.
Meanwhile, add sausage to a large sautè pan over MEDIUM heat. Cook, stirring to break up, and continue to cook until no longer pink. Use a slotted spoon to transfer sausage to a paper towel lined plate to drain. Pour off any grease from pan and wipe down with a paper towel. Return the pan to the heat and add the butter. When melted, add the onion, apples, celery and carrot. Turn the heat up to MEDIUM-HIGH and cook, stirring frequently, for about 7 to 10 minutes or until veggies and apple are fork tender. Add garlic and parsley and cook and stir for another 1 to 2 minutes. Add the sage, poultry seasoning, thyme, marjoram, salt and pepper. Mix well to combine. Remove from heat.
Preheat oven to 350 degrees F. Coat a very large baking dish with non-stick cooking spray and set aside. (Note: stuffing can be split between two dishes).
Transfer toasted cornbread and French bread to a large roasting pan or very large mixing bowl. Spoon the vegetable and apple mixture and the cooked sausage over the bread and mix well. Add the beaten eggs and stir to combine. Add 2 cups of the chicken broth and stir well. If you are making this a day ahead, stop here and refer to Make-Ahead Instructions below. If baking right away, add additional chicken broth, a little at a time, until you've reached the desired consistency. Stuffing will dry out a little bit as it cooks but you don't want it to be too wet going in to the oven. I don't recommend adding more than a total of 3½ to 4½ cups of chicken broth.
Transfer stuffing to the prepared baking dish(s) and cover with foil. Bake, covered, at 350 degrees F for 40 to 50 minutes. For a crispy topping, remove the foil during last 15 minutes of baking time, or place under the broiler for a couple of minutes before serving.