OK, I just did a lot of power planning for my camp, so I can help a little.
First read this page: http://www.templetons.com/brad/burn/burn-power.html
Something else I learned is that big batteries take a long time to recharge, and this is limited by the output current of your charger. Cheap chargers put out like 6 amps which means it will a full day of generator use to refill an 80Ah battery. My camp just purchased this 40 amp charger so we can refill a big battery in an hour or two. Ask me next year how well it worked out on the playa. http://www.amazon.com/Black-Decker-VEC1 ... sim_auto_5
(it was half price when we bought it, you can probably find it or something similar for $80 somewhere). Or as Figjam says you can try recharging off the motor. I have no experience with this.
You can rent a small generator from a place like hertzequip.com for about $150 a week. Fuel consumption on these was something like 0.8 gallons per four hours. You might save money with such a scheme compared to your RV genny if you are running it a lot, and it will probably be quieter.
Strings of solar LEDs can be found for $25 and are pretty good. Not super bright, but a few of them will light up a small camp well enough that you won't trip. My camp will be using battery-AC LED strands for a few hours each evening, and then switching them off and relying on a small number of solar strands from midnight to sunrise, or so.
To do this proper you need to plan your loads in terms of battery amp-hours. One hour of 60W stereo use is 5 Ah at 12V, and 40W of lighting is say 4Ah. So if you want stereo for four hours a day and lighting for 4 hours an evening, you need 36 Ah of battery per day. So an 80 Ah battery would work, if you recharged it fully every day.
To charge via solar, if you have a 30W panel (about $250) and get ten hours of sunlight a day, that's 300Wh, which at 12V makes 25Ah per day. It's in the ballpark of being able to maintain the charge for the above scheme if you were to cut your power consumption a bit.