Jobert gave you good advice. I also moved the old 13,500btu front heat pump to the rear bedroom and installed a new High Capacity (15,000btu) Heat Pump on the front.
The hardest part of the install is getting it on the roof. We used a very long ladder against the roof. Kept the A/C in the box and tied a strap around it. Then we connected a long tow strap to the box and two of us pulled it up the ladder.
All the new Dometic A/C systems come set up for the new CC2 programmable thermostat. You have to purchase a retrofit control board that goes inside the A/C to be compatible with your 5-button Dometic thermostat. PPL Motor Home parts was very helpful in ordering the heat pump and the control board.
Your other choice it to purchase two (or in longer coaches three) new A/C units and a new programmable thermostat. Then you also have to make it compatible with your furnace.
Like Jobert said, there are dip switches inside the A/C that must be properly set. These will be well covered in the install instructions. If you move the front A/C to the rear you will also need to reset the dip switches so the zone is correctly set.
I made a detailed writeup with pictures when I installed mine.
Let me know if you have any questions.