Congratulations!!!! I bet you are extremely happy and relieved. Hopefully your SO is 100% completely on board with this. There have certainly been many instances when a partner seems completely okay with it at first, but then the grieving period starts for them where they realize they are losing the persona they've spent years loving.
Just be sure to understand where they are coming from should it ever come to that. Even my parents and family, who were 100% supportive, never once cried or displayed negative emotions in front me, and even paid for some of my surgeries, later told me that they did experience a grieving period without my knowledge. Everyone will go through it.
But I am so happy for you!