Yes, I think 2 hours will be plenty. The domestic terminal is really easy to get through. Once you check in, it will be very easy to get through security and walk to the gate. I would say 10 minutes from security to gate.

Going from international part of GMP to the domestic is also easy, but it is a bit of a walk. I usually use the underground tunnel that connect the two terminals. They do have moving walkways there, but it will still be a walk. As of Aug 2013, a portion of the walkway towards the international terminal is under renovation, so it is a bit congested but still easily walkable. I would factor in 20 minutes to walk from one terminal to the other.