You can get turkeys at the store, if you get frozen make sure to have several days to thaw. Also recommend cooking in a bag, Reynold’s Oven Bags, cool much faster and don’t have to worry about basting/drying out. Also, recommend getting a good instant read thermometer, I would not rely solely on the pop up timer. Always cook a turkey to temperature, the recommended times are often not accurate, start checking temperature 30 minutes before end time.

I usually do 1-1/2 to 2 lbs per person, this will give you tons of leftovers, go closer to 1 lbs/person if you don’t want leftovers.

Final option is to buy a cooked turkey and pick up on Thanksgiving, many places do this.

Also, if you want a fresh turkey you might have to preorder a couple weeks ahead. I would check with your local store.

I have never done a test run with a turkey.