I have been doing 28 -33 lb birds for several years. I have found that if I do not brine the turkey is guarenteed to be dry and unimpressive (other than looks). If I brine for 24 -48 hours, my turkey is moist and delicious. I have had lots of people oohing and aahing about how they never thought turkey could be so good.
I use Poultry seasoning in my brine plus a bit of extra sage.
As for cooking time. I preheat the oven to 450. I put a quartered lemon, garlic, a quartered onion and