Everything I have seen on it points to the fact that things can get better with effort. Since like any mental status it has a spectrum of severity.

One of the main problems with Narcissism is the lack of self awareness as well as the lack of mind-fullness of those around. It’s going to be pretty hard to get a different perspective on behavior without an outside reference.

I’ve heard a story a people who was narcissists improving, but I have no idea of it was self driven or with assistance.