If you haven't done one, I'd suggest a test. Turkeys are pretty cheap and I would do a test.
Is it absolutely necessary? No.
If you get a good bird (look for one that doesn't say 'enhanced with x% solution) if you can or one that says water retained up to X%. The enhanced means they've brined them already.
I'd also smoke it not roast it. 400 would be roasting. Go for a lower temp, 275/300 or so and get a reliable temp thermometer and shoot for 160 in the breast.
Don't wait for a holiday to practice. If you want it to come out right under all the Holiday stress, then a little practice is in order.