I'm running my first marathon on Sunday. I read on the internet that you should eat 4 grams of carbs per pound the day before the race. At 185 pounds, I would have to eat 740 grams of carbs! Does that sound right? What would I even eat to get that much? 4 bagels (which is a lot of bagels imo) is only about 250 grams of carbs.
My first marathon was 4 months ago. I did not worry about what I read on the Internet, but rather made sure that I felt good. Above all, I tried not to mess with my eating routine. I was much more afraid of upsetting my stomach than of running low on carbs. I even had a glass of wine the evening before because, well, I liked to.
Granted, I did eat lots of carbs the evening before (300 g Pasta/170 lbs body weight), but more importantly, I went to the restroom well before the start of the marathon. Also, I started refreshing early during the run, but stuck to bananas and water. Energy gels can be tough on your stomach if you're not used to them.
In the end, I found it easy to deal with energy consumption and dehydration. Even motivation was OK (though it does get boring after 4 hours). My problem was my left knee, and it was hard to stop after 30 km, even when I was feeling pain. But then, others had problems with chafing nipples. There are so many ways a marathon can go wrong.
Don't worry about the carbs (unless you really have issues with blood sugar)!
Stick with whatever routines you have used to for your LSR/long-distance training! You know it works. "If it ain't broke..."
It is a very, very common mistake to overdo all the preparations for the first marathon... usually with less-than-optimal results.
I did that as well for my first marathon: Eating a lot more pasta than usual (almost the double than normal ration for a 28-30 km LSR), almost no meat or protein the last day (I usually just eat whatever is for dinner), getting up very early to eat the breakfast 4 hours before the race (I usually eat a light meal 2 hours before the start of LSR), etc...
The end result was that I felt stressed and very nervous before the start of the race: normally I would know pretty well how my body will react to the long distance - but not here as I effectively was in untried waters. And the result was as expected.
So just stick to your usual routines for a LSR! There are no need for alcohol, big steaks, fat ice-cream or late movies, but other than that it is business as usual. This way it is so much easier to enjoy the race :-)
And good luck..