I agree that your GPA is not so much of an issue. However, if you are considering a career change, there are a couple of things you should consider:
Age it's not a problem on its own. However, you should consider having a prolific profile on research publications to get hired (tenured). As you start your career late, you would be at a disadvantage.
That's why it is essential to connect with professors that can guide you and support you in the way.
There is a significant problem in the academic job market: too many Ph.D. holders for the number of positions available to hire them. That sucks, but it is how things are.
You should explore your advantage: you got experience in finance. That's something that makes you different and could provide an opportunity, both for you and potential advisors.
I do not mean to discourage you in your dreams. Just giving some information on time. With hard work, you can make it.