I live close to a trail and have been doing traverses over a local mountain range, eventually increasing milage by walking off the mountains on the other side and going back up and walking home again.
My longest day has been 55Km (34miles) with a bit more than 5200m (17000ft) elevation change. It wasn't a race, just something for myself and I did it in 10 hours.
Some of the things I have found, which might, might not be useful to you and your trek. Take what is useful to you, ignore the rest of course..
I never ran, only walked, at an average speed of 5.5Km/hr or 3.4miles/hr). I had done days where I went faster, allowing me to go a bit slower but longer for this day.
For me the trick was going fast but not too fast and be able to sustain that pace, almost continuously. I did one 10 minute break, and two other 5 minute breaks, mostly to change some kit. I try to keep a fairly fast pace on the climbs, recovering on the flats or descends.
So that means eating and drinking on the go, and also not stopping all the time to adjust your gear. I found during other days where I go shorter but climb harder and walk faster, that stopping to eat, stopping to navigate, stopping to get something from the bottom of your pack, etc. is one of the greatest time eaters. It is very hard, for me at least, to walk faster than an average 5~6Km/hr (3.5ml/hr) so my fast time comes mostly from consistency.
I mostly wear a base layer with a big ½ zip, a wind shirt with a hood, a buff/thin balaclava, and a cap. With this you can alter a lot of your temperature while walking. Neck and forearms are for me great thermo regulators. Zipping/unzipping chest zip, exposing forearms, donning my hood or not, etc. I bring a rain shell, but often don't wear it unless it gets around 0~6˚C (32~42F). I just get wet and because I'm hot I'm ok. At those times I do have my thin balaclava/buff and hood up to keep my neck and head warm. What also helps me a lot if at half way I can change into dry socks (smart wool PHD's as well) and a dry base layer. Really, really makes me feel as if I just started and I can highly recommend doing this if you can afford the weight.
I like shorts but with the bugs and rough plants and dirt I often wear a thin long pants. If I do wear shorts I wear dirty girls gaiters to keep some of the dirt out of my shoes so that I don't need to empty them out every hour. Though you might be forced to, if the trail you will do is that sandy. Anyway, taking care of your feet sooner rather than later if something is bothering them will prevent that small irritation from grinding you down to a snails pace (or a full stop of course).
For hydration I have water mostly. I don't really like sports drinks, but you do need the minerals of course. Here in Japan we have hard candy with salts in it. I take those and hydrate. I have also made tea with honey and salts which you could try as well, but if you do I would try that a couple of training sessions before so you know how your body responds to it (too much salts and you might get the runs for example).
For food I had a lot of dried fruits (dates, figs, raisins, berries) some cliff bars, nuts, and probably bananas although they are heavy. I personally liked the dried fruits better than the carb gels etc. that runners often take. If you have trained a lot already and you don't overdo it with your speed your body will not eat into its glycogen storage as much. Even then you should probably try to eat consistent small amounts of carbs. I eat and drink something every 30/45 minutes I think. If I eat bigger, heavier carb/calorie bombs I don't feel as 'light' and need to stop to eat and rest a bit. So I keep it small and light and as natural as possible. If the weather isn't too hot I love to bring lots of chocolate though.
Not sure if that is useful at all. I would test any changes in the system or clothing you already have beforehand so you know if it works for you or not. Since you run you probably know better than me to listen to your body seeing what you can keep up with, and when you can sometimes push a bit. For me the last hour or two were absolutely killer. Shaking legs and bruised feet on a steep descend and it was mostly autopilot.
Hope you have fun out there!
edit - think Eugene above did a better job of talking general principles, especially regarding hydration/nutrition (don't get into a deficit, it's harder to re-hydrate than to stay hydrated etc.).