Saute the sausage in a frying pan until cooked through. Remove the sausage and process in a food processor until finely chopped. Leave the oil in the pan you cooked the sausage in and add the butter and olive oil.
Finely chop the onions and celery in a food processor and add to oil and butter. Chop the sage leaves and add to pan with salt and pepper. Saute until onions are translucent, about 5 minutes.
Put the bread crumbs into a large bowl. Add the turkey stock to the bread crumbs and toss until completely absorbed. Add the rest of ingredients and mix thoroughly.
If you are not cooking the stuffing in the turkey, add 1/2 cup of additional stock, butter a casserole dish and bake uncovered at 350 for 30 minutes.