Battery life and more questions

I have so far only stayed on sites with EHU but would like more flexibility.  I have a 2002 Elddis Autoquest 400RL.

1. Roughly how long does the leisure battery last without EHU?  I.e. with minimal use for lights etc does it last days or hours?  And when the site info shows a battery symbol, does that mean you can charge your leisure battery there?  

2. Is there a way to tell if your gas is running low?

3. I haven't used the shower yet as I'm worried about damp mould.  It seems as if the water from the shower would make the whole bathroom wet.  Do you just have to wipe it all dry every time?

4. In the bathroom the light doesn't work.  Presumably the bulb needs replacing - can you tell me how to access the bulb to change it?

5. On very basic sites, do they usually have water?