They are cheap, get one for each battery.  If you don't even know if you have a 2nd battery, that suggests a pretty low level of knowledge about your vehicle.  You should spend some time learning about it before relying upon it far from home.  It's 35 years old and getting towed home for minor stuff constantly will get old. And expensive.

This is a great idea.  I am not sure if 1) I have both a house and chassis battery or 2) they are tied together or 3) they operate independently. The parasitic drain makes me think they are tied together.  Would you guys think I need 2 battery disconnect switches or can I just put one on the chassis?  I don't really know where my house battery would be stored.  But the fact that my lights work when not connected to shore power means I have one, right?  

I recommend state parks; that’s what we do almost exclusively, and I build my trips around them. The cleanliness, the scenery, and the presence of trained, uniformed staff to help create a safe, quiet and family-friendly environment is essential, and state parks do better with that than most other places (especially for the money—whole lot of bang for your camping buck!). 

I’m sure there are exceptions, so always read reviews prior and do the research. 
 

Final thought: I find campground camping anywhere far better during the weekdays, rather than the weekend, if possible: much quieter and more relaxing.