It is very very easy than what you are afraid.

If she is already having an RP here, the process become so easier that the authorities need not change her ID number too..she will keep the same.

I thnk you may need NOC from both employers,  salary certificate, bank transfer certificate, sometime the Kahrama bill to show your proof of residence, your marraige certificate to show she is your wife..

Sure, I can tellyou,, the process is much much easier than a new family visa to a new entrant in Qatar