Since this is your first marathon I suggest you bring a Powerbar or something to nibble on at around mile 15 (most first-time marathoners will need to do this). Work yourself up to 22-23 miles the week before the race and your adrenaline will carry you through the marathon. Get a good amount of water and potassium in you before the race, especially potassium, if you get a side cramp in a marathon, it's over ,you'll be walking to the finish. Also be wary because there are a couple people each marathon that will piss/shit themselves while running so as not to stop and lose precious time and rhythm. Stay in a relaxed rhythm and run as close to even mile splits as possible. Naturally, you will run the first mile faster than your splits since virtually everyone else does it and you don't want to get trampled. Just don't get carried away with it and don't run it 30 seconds faster than your targeted splits.
PS Ex-runner myself, once ran the 15K (9.3 mile) Jax River Run at 1:01:32. Too bad that was 80 lbs and 2000 beers ago.