Well, he did say he's running his "first marathon"..awesome goal, that was my goal in 2009 and I did it. I finished the Richmond marathon in 4:55:28, looks like you're on pace for a time around there too. Trust me, leave the damn phone at home, enjoy your experience. This is your first marathon, It will be life changing. This Saturday I start my first run (only 7 miles) as the start of our team's 6 month training for the Marine Corps Marathon on Halloween this year. This will be my second marathon, with my third coming 2 weeks later...if my knees survive.
My first marathon, I did everything the exact same on race day, except I "did the salt" at mile 18 and HOLY HELL that was amazing!. Get some McDonald's salt packets and eat them later in the race, I'm prone to cramping, even sitting in a chair, so the salt helped me finish the last 8 miles. I still cramped up to hell, but I finished the thing.
I hope you enjoy running as much as I do. Take your tunes (If you use them, I didn't until mile 23), take your Garmin, leave the phone at home. Do you really want to carry an extra 6.0oz for 26.2?
The 1/2 way point of a marathon isn't 13.1 it's mile 20. Here's some advice if you're struggling the last 6 miles and may miss your time goal by a couple minutes. Count every person you pass, and subtract one for everyone that passes you...it'll take your mind off the brutal last miles, and it'll speed you up just enough. You've put in the work, now get out there and kill it.
BTW: Which race are you running? Feel free to PM me if you have any questions.
...I've been drinking...last night of a good bender for a good 6 months...f-ing training.