A substantial gas leak you generally could detect by smelling carefully around the lower vent. A gas leak would more typically lead to a terrific explosion rather than a sustained fire; think more of blowing the RV apart, rather than setting it aflame, or so I've been led to believe (and seen pictures of). Of course, neither a fire nor an explosion is a desirable outcome!
Keeping critters and crud out of the burner and chimney assemblies and keeping the refrigerant inside the refrigerator piping are the main aspects of maintenance, so far as I know. Well, keeping the food storage compartment from getting all smelly and science-fair-project-y is also wise.