Newbie in need of advice...PLEASE!!

Hello, my wife and i are newcomers to touring and have just bought a 2000 Coachman Amara 580/4, it's in great nick but need some help and advice on how to use some of the equipment, this might sound really basic stuff but am i right in thinking that when i am towing with double electrics i switch the power source controller to car mode so that it cools the fridge etc and charges the vans leisure battery enroute?, and when i get on site i hook up to 240 volts and switch to van mode so that the leisere battery is continually charged?, the problem i have is i have no power at all from my 12 volt supply and i don't know if i have done something wrong and drained the battery which was almost brand new when i bought the van a month ago. Will the van have an on board charger?, and if so could there be a problem with it?. We are going away again in a fortnight so any help would be very much appreciated because if i don't sort it i just know the power on site will go off and we will be left in the dark, please excuse my naivity but like i say we are newcomers and want to learn. I also need advice on the heater, it works fine but the controls confuse me, but thats for later, the battery problem is more important. Thanks in anticipation. Steve and Debbie.