I recently (last week) completed the 24hr Le Mans endurance race single handed in a single sitting, and it certainly is do-able, although I completed mine in 26hours
My biggest reccomandation would be to start staggering your sleep pattern, until you are in a position to comfortably able to wake up at 2:30pm, giving you 30mins to prepare yourself to start racing at 3:00pm. The reason I say this is because of the night section, which honestly just drags on and on and on and on and... ok you get the picture haha!
As some of the guys above have said, and you yourself have said, plenty of energy drinks (red bull, monster engery, rockstar - whatver really) plenty of coffee, some sugary snacks and a damn comfy seat will do you for the entirity
Don't be afraid to pause for 2 minutes here and there for toilet breaks (unless you intend on wetting/soiling yourself??

) As mentioned, do the Le Mans enduro first and see how you like it, personally I loved it, kept it nice and competitive by doing a couple of practice sessions to get my car close to the power limit of the other cars. In the end I finished just 2 laps ahead of 2nd place.
Trust me though, start at 3:00pm, and be be prepared for a VERY long night of racing in the pitch black!!! A Premium car is definately the way to go, as far as the headlights are concerned, but I would strongly reconsider on the Peugeot 908 though, as the main beam is about as good as driving by candle light (seriously!) Do a few practice sessions on either Nurburg or Le Mans in the dark and see which car offers you the best visibilty in the dark, and go with that, as you will be able to keep your lap times up, instead of slowing down because you can't see anything until its too late haha. It's not worth buying the Audo R10 either, as that is the prize for completion of Nurburg 24hr (or so I'm told!)
Obviously the Le Mans circuit will be a walk in the park for 24hrs compared to the Nurburg though, so I hope you know the track well

Best of luck, and I look forward to seeing how you do, when you get there!
I'm already lvl 38, and working towards lvl 40 so I can attack the ring before getting B-Spec Bob to follow in my footsteps
