Price to replace a knock sensor in a 2002 Chevy silverado.
Some where between zero and a million dollars. Sorry, Paul this is one of those things you will just have to do yourself . Any decent shop near you can do this but make sure that is what you really need instead of just throwing parts at the vehicle.
Someone here might know the typical time (hours) it takes to replace them. I’m pretty sure on that model, you have to remove the intake manifold to get to the knock sensors. So, it won’t be super cheap.