I want to endorse what Elena said above about your base layer. There is no need whatsoever to take two separate base layers. I use my base layer for sleeping (basically pajamas), but also wear it under my hiking clothes on cold mornings and evenings. The hiking clothes plus my insulating jacket (and maybe rain jacket and pants) keep the base layer from getting dirty or picking up food smells (which I understand is Philmont's reason for separate sleeping clothes). I never hike in my base layer, so it doesn't get sweaty.
I also endorse the suggestions for several shorter "shakedown" trips first. You don't want that long and difficult trip to be your first one! You need to test your gear thoroughly so you know how to use it, practice packing and unpacking, pitching and striking your tent, keeping dry in the rain, and lots of other skills. It's best to start learning these skills somewhere like a state park or national forest campground, or even your back yard, where you can bail out to your car if things go bad. Then try a trip that's just a few miles from the trailhead. Be sure to plan a few of these "shakedowns" in inclement weather.
Those new SMD tents mentioned above won't be available until at least July, so keep that in mind if you decide to order one.

