POWER PROBLEM WITH NEWMAR, NEWBIE

Thanks, batteries are only 1 year old, both of them, System was working fine then it just stopped while driving. When I disconnected from shore power the lights worked and steps worked. Then about an hour later nothing worked. The inverter circuit breaker, where is this at. Can you walk me through how to trace this down. Remember guys, I am fairly familiar with 12 volt auto and 110 house current but this is a mix with inverters an converters and this is all new to me.