They have a battery, most of the time they say the life is anywhere from 7-10 years but thats useally never the case.
You can not replace the battery itself on the GM ones, nor can you on pretty much any other vehicle as they are sealed inside the sensors case.
Its not worth it to spend the money and replace them all if they still work.
Just have a local tire shop change the sensor. I change them all the time at work, either the customer buys the sensor themselves or we buy them and install them.
A dealership can sell you one, but they charge an arm and a leg for one, so we use NAPA sensors and never have an issue with those ones. After the shop installs it, they should be able to reprogram it to the car. Ask before hand if they can program it or read your owners manual to see if you can do it yourself as some cars can do it that way.
