OP here: thanks everyone for all of the advice. I am going to double check with the store to ensure that the turkey is fresh, not frozen to ensure that I won't need to thaw for days and days. I am going to brine, using a cooler, since there is LITTLE chance that the turkey will fit in my fridge. I may go for a 20-22 pounder, since we probably don't really need 24. And I will definitely buy some gravy from Whole Foods and make sides in advice.
As my mother says, "you only make your first turkey once, so stop worrying about it." Smart woman.
Be aware that for a grocery store turkey, "fresh" still usually means frozen. "Fresh" turkeys can't be frozen below 26 degrees. Freezing point for water (which makes up most food) is 32. So "fresh" turkeys just can't be frozen that much. They'll thaw quicker, but they'll still need some thawing. ("Frozen" turkeys are often frozen and shipped at around zero degrees. They can need days and days to thaw.)
If you want a truly fresh, never frozen turkey, you're probably paying some serious coin for straight-from-the-farm. (Either at a farmer's market or at a place that will order them, like MOM or a butcher shop.) But even for a grocery store, "fresh" is going to be better than frozen. But you'll still need to thaw for a day to be sure.