Should I leave a secure but possibly unsustainable career for a riskier but potentially rewarding one in a new domain?

I’m currently making a great salary in an industry and role I’ve had for 10 years. It’s stable, secure, and interesting, but due to its professional service nature is also stressful, reactive, and I don’t have much control over my projects. I’d also have to go back to school for 3 years in order to ensure career longevity. However, I now have an opportunity to work under a former, trusted colleague at a new part of the company, but in an entirely new role and career path. The specific domain is completely new, and the role is too; I’d be losing my old expertise, knowledge and relationships. I’m 35 and about to be married and start a family; it feels risky to make this move, particularly with the political uncertainty, but in the long term, I know I need to make a jump like this. But it is risky and I have a lot to lose; and I’d have to master a new domain quickly. I work for an excellent company but stuff could get restructured. Would prefer to not give more details so as to preserve anonymity. Thanks in advance.