Here's the recipe that I used. Per some comments there, I added garlic powder, salt, and black pepper to taste to the gravy. After pouring the turkey, gravy, and spaghetti mixture into the baking dish, I sprinkled some Italian bread crumbs on top before putting it into the oven. I also baked it for 40 minutes instead of the 60 minutes the recipe calls for. There were some leftovers, but not as much as I thought I'd have.
I didn't add them, but green peas would go nicely mixed in with everything else before putting the baking dish in the oven. Sauteed mushrooms would also be a nice addition.
And the gravy would be excellent in a chicken pot pie.