A little more information would be helpful. Such as which RV you have and which brand A/C you have.
If it's a standard roof mount RV A/C, they're pretty easy to replace. You take the grill off the inside and there are power and thermostat wires (if it's a t-stat operated unit). There are also 4 bolts that hold it to the roof. One you unhook the wires and remove the bolts it pretty much just lifts off the roof and the new one will sit right in it's place.
Salem 29RKSS Pushing a GMC Sierra 2500HD!
Gotta go campin!