what training plan are you using?
hopefully one that adds to your long run incrementally, one that adds some back to back longer runs together, one that pulls back mileage every four weeks or so (a recovery week), one that tapers before your event
as you've been running for awhile, but shorter distances, your long run will be the most important run of the week- insure you're well rested, well fed and hydrated before that run
as mentioned above you have time now to figure out your hydration and calorie regime- you'll want this well dialed in before race day; if they work for you (they don't work for everyone)- liquid calories (mixed with your water) are easy and easy to regulate- Hammer Perpeteum, Tail Wind, others
elite runners don't have to worry much about calories in just 26 miles, mortals do
good luck!