Cut acorn squash in half, and scoop out the seeds and membrane. To make this easier you can poke the acorn squash with a knife, microwave for 1-2 minutes, and then cut in half. Discard the seeds, (or roast like pumpkin seeds). Bake the squash halves cut side down on a rimmed baking sheet for 30-40 minutes, at 350°F, or until soft, but not mushy.
Saute sausage until just cooked, and then add onion, celery, carrots, and seasoning. Cook, at med-high heat for 10 minutes.
Add water, reduce heat and simmer for 5 more minutes, or until all is tender.
Stir stuffing into mixture (adjust seasoning if needed), then spoon into the cooked squash halves, packing down slightly, and mounding on top.
Bake at 375°F for 15 minutes, or until slightly browned on top.