Is it sufficient to just turn the battery disconnect switch (the one located at the entry step) off prior to installing new house batteries? Or should I also unplug from shore power?
Definitely unplug. The salesman switch is on the OUTPUT side of the batteries. Inverter/chargers are directly wired to batteries.
When you unplug the coach, make sure your inverter is off, i.e., not inverting before removing the ground cable.
Don