Place the mushrooms into a microwave-safe bowl. Add a splash of cream sherry and nuke until cooked, but not wilted, about 2 minutes.
Heat the oil in a large skillet. Saute the celery, onion, and garlic over low heat, for 10 minutes. Do not brown. Put them and the mushrooms into a large bowl.
Break up the sausage and brown in the skillet. Cook about 10 minutes, breaking into small pieces, until fully cooked and lightly browned. Add to vegetables.
Add in the apples and cranberries, and mix. Fold in the bread cubes. Add the salt, thyme, sage, and pepper. Mix gently. Add the sherry and stock and toss until coated.
Preheat oven to 325F. Put the mixed stuffing into a roasting pan (should fit just about right). It needs to be baked for 45 minutes, but just about now, the turkey should have pan drippings available, (1/2 hour before completed cooking.) Pour some of the pan drippings over the stuffing (a light coat is about perfect, maybe 1-2 cups total) and bake the stuffing for 45 minutes, loosely covered. It should be done just about when the turkey is carved.
Makes a lot of servings, probably about 20.