Gas tank location on 2000 silverado and how do you drain it got some water in gas so got to get it out?

Unless there is a ton of water in there then I would just add some gas line antifreeze and run the truck until the tank is almost empty. The only would be to either siphon with a pump (you will need to take the screen out of the filler pipe) or drop the tank. Look directly underneath the filler pipe on your truck for the gas tank. Again, if it was me I would just run it out.