Such total nonsense that I would recommend you avoid them like the plague, they have no idea what they're on about.I've found a place in town that can help me with the battery and isolater install, however, they told me that if i don't use the exact same battery as the one i currently have (toyota true start), they can't guarantee that the system will work properly. Does that sound right?
No one local is likely to have a clue about this stuff.
Spend some time googling and reading past threads on these topics and you will likely know much more about DC deep cycling, than anyone automotive oriented in a 200mile radius.
You figure out what you want, select and purchase the components yourself, and then just pay for the wrenching labor following your instructions.
Never mind about any "guarantees", completely irrelevant.