Check what the roof frame spacing is on your coach and I think that you will find that 14" is approximately the distance between framing members. If that is the case, than all you have to do is decide where you want to cut the hole. Naturally you will have to screw in additional framing members for the sides and to beef up the roof frame for the additional weight.
Getting power is one issue. Your second electrical issue may be how you connect this new AC to your existing thermostat or if you go with a separate thermostat. You also may have issues with an Energy management system in your coach.
Have fun.
