Glad it is working for you!.
I'm considering an upgrade like this too (from my Xantrex 2012 to a pure-sinewave Magnum).
Have you confirmed that the factory cable size is sufficient (i.e. 4/0 AWG) to support the "larger" 2812 model?
If your Coach, like mine and came with a 2,000W inverter, the factory wire gauge may be too small to swap in a larger unit (like a 2,800 or 3,000 W) without the risk of overloading the wiring if maximum output was sustained for a long period.