RE: Missourri Whitetails
If this is a guided trip, my guess is that you will be hunting in the northern third of the state and will be hunting land that is being manage for trophy deer. It should be fun. I never heard of that outfitter, however I can't name you even one outfitter in the state.
MO, especially the northern part can compete with Iowa, IL, or KS as far as big bucks. Our only problem is that most bucks never reach the age that is needed to have those heavy antlers.
I live in central MO and we have some nice bucks here as well, but the northern part of the state has an advantage over us in their antler potential.
Weather wise, (I am assuming this is during our firearm season) be prepare for an extreme of weather. It may be near 80 or below 0 with snow. On average expect lows in the 20s and highs in the 50s. We often have damp cold weather that can feel very cold.
Good luck.