Calculating life expectancy

I am doing a research project and I need to calculate the life expectancy of a group of musicians. I have a spreadsheet with 400 people and their ages. More than half are still alive. What is the best way to calculate the life expectancy of this group?

Also, I have very little experience in statistics so maybe you can direct me to a book or website that explains this in detail?

Thanks for the help,
What about the Kaplan-Meier estimator? From what I've found that seems pretty straight forward and easy to calculate. Is this a good way to find life expectancy?