Hi RS. I made the decision to go NC with my mother about 6 years ago. It was NOT a decision that came easy. After several talks with different therapists, reading books, and boards like this, I began to realize that it was the only way to be truly free of her torment. Hard choice, because no matter how badly our N parents treated us, it's impossible to escape the guilt of going NC. I kept feeling that I had done something cruel, and of course M knew how to work those emotions, and started sending me letters and emails trying her best to guilt me. When I refused to respond, she went after my husband, writing to him and trying to turn him against me.
Going NC also heightened her smear campaign against me. For years now, she has been telling other family members that I "disowned" her for no reason, that she loves me, I'm her favorite child, how could I be so cruel, etc. Someone said something in another thread that really helped me - anyone who would fall for such a smear campaign is someone we don't need in our lives, anyway. Those words REALLY helped me.
I have to say, that while going NC has caused a lot of internal conflict, being free of the constant torment has far outweighed any emotional struggles that I've had. And the emotional aspect of it has gotten better over time, the more I talk to other people, both victims and professionals, who have validated that NC is the ONLY way to deal with a narcissist.
One warning. Ns will not just sit back and accept NC. That means losing power and control, and they WILL fight back. My mother never stopped sending the nasty cards and emails. She refused to just let it go. She is now terminally ill, and still trying to guilt me, using other family members as tools to hurt me, changing the will to hurt me, it goes on. Hubby and I are quite convinced that we will receive a letter from her after she dies. It would not surprise me at all if she has written something designed to guilt me into dust, with instructions for my father to mail it when she's gone. Of course, my F would think it's a letter telling me how much she loves me. All this is speculation at this point, but would perfectly fit the pattern of her behavior over the last 40 years, so we see it coming. One final posthumous attack. Control from beyond the grave.
Going a little off topic here, but my point is that they NEVER give up. Since you're planning on moving, try to move as far away as possible. Physical distance really helps, in addition to emotional distance.