Back to the original question... :)
I think the new rifle question has been answered and I'm with the .338 folks. However, I do love my .375 and it whacks whitetails just fine.
Two biggest things I'd recommend is a second scope with rings that you've already zero'ed. Scopes (IMHO) tend to be fragile. Second, get with your guide on the first day and work on him talking you on to various objects. My guide had superb "game eyes" and could spot critters much better than I. We used a clock and distance method and it worked well. He'd say "3 o'clock, 75 meters" and I could then know where to look. 12 o'clock was always where I was looking, so 3 o'clock would be to my right, 6 o'clock behind me, etc., etc.