Aging Parents

My parents will be 70 years old next year. They’ve done a pretty good job of getting ready for retirement and have set up a living will, “Loving Trust” account. I have been told that I will be the executor, along with my younger brother who lives in Indiana with them. That’s all that I know. At what point do I need to actually know what their plans are? Is there anything that I need to be aware of to handle this for them?