Congrats on the new bag. The Marmot is really well made and should last for years.
This may be a lot of redundant information, but here goes anyway:
Do yourself a favor, and pick up a fleece liner to carry along on your trip. It will add a significant bit of warmth to your bag if you should need it, or you can use it as a light blanket if you take an afternoon nap or it's unseasonably warm at night.
Also invest in a waterproof stuff sack. A wet sleeping bag can take days to dry, and getting rained on hard, or falling in a river on the hike in can ruin a trip.
Before bed: Change your socks and underwear. Put on clean dry ones.
The moisture and body oils in your undergarments will be more difficult for your body to heat, and can make an otherwise cozy evening downright miserable. If it's really cold, wear your beanie to bed.
Wool is your friend, and there are a lot of really good synthetics out these days as well.
For a mat, a lot of good ones were mentioned here. I've used the same Therm-A-Rest since 88. It's been all over the western US with me, most of that while backpacking (I averaged 50 nights a year from my early teens until my mid 20's when I got married).
For a failproof mat, that doesn't require holding any air, and is lighter than any of the air filled ones, look at a closed cell foam mat. They're much less expensive, but highly effective. They do take up a bit more space, and aren't quite as plush but they will absolutely keep you warm.
For your water: invest in a wide mouth Nalgene bottle with a screw on lid. At night, turn it upside down and keep it next to you. Water freezes from the top down, and if you are wanting a drink, you don't want to have to chisel it to get a sip. The #1 thing making folks sick at altitude is directly related to dehydration.
Enjoy your trip, sir!