All disk brake conversion kits are pretty generic to any brand be it Montana, Cedar Creek, Jayco ... so don't get hung up on guidance for your specific unit. The brake parts themselves that replace your electric brakes are an easy swap on your Dexter axles with nothing special involved for Montana specific. Deciding on just what path to run your lines and where to mount the actuator is where differences in install come into play. Most mount the actuator in the front storage compartment. Wiring the actuator is very simple as in 4 wires ... power, ground, breakaway switch, and controller. You do not need to purchase a breakaway battery as you already have that power source from your house batteries. The extra breakaway battery is for installs like standard horse trailers where there is no house battery. Here's an install I did several years ago on brand X. Other than 8 lug rotors, your unit would be no different.
https://www.montanaowners.com/forums...ght=disk+brake
PS ... Just my personal preference, but stay away from all rubber lined kits and go with hard lines as much as possible.