battery disconnect switch

I want to put in a battery disconnect switch and need to know if the pod battery negative wire is the ground wire, since I understand one should remove the ground wire first when removing the battery. Having had a car with positive ground at one time, I like to be double sure of things. Excess caution, you know. Would appreciate any guidance offered. I am always trying to learn new things.

Thanks for the info, and now that I have put the switch on the battery box, I have another question. The battery is only on if the red key is left in the switch, as removing the key shuts off the circuit. Is that correct, and if so does that mean if I want ref. on 12v while driving, or if I want the coach battery to be charged by the tow vehicle that the key must remain in the switch?  That seems a bit odd, but doable. I thought about reversing the wiring on the switch posts, but it seems that would make no difference. However, I am electrically handicapped and never can do much with voltage things. Would so appreciate a shout out about this, so I can keep on working down my list of must dos on my pod. By the way, the positive ground car was not an MG. It was probably the old 2 cyl. French Panhard, but it was way too many cars ago to trust my memory.

Thank you so much for the quick answer. All is well with my installation and I managed to do it right. Wow! This forum is such a great resource!