[faithfulfrank]

Bob,
This is very easy. First, make sure your sprinkler system is off. There are a few ways to do this, but the easiest is to just go to your control panel or control box and turn it off. If you are sure that today is a day you will not have your sprinkler system turning on, then you do not need to do this.

Next, get a small hand trowel and dig around the sprinkler. If you have a small green donut around it you can lift it off and set it aside.

Dig down until you see the bottom of the sprinkler head. Below it you should see a PVC elbow that is threaded going into the bottom of the sprinkler head. Dig a little deeper so that is exposed.

Once the dirt is away from the entire sprinkler head, and removing it will not allow dirt to fall into the pipe, unscrew the sprinkler head from the threaded pipe. Before you do this step, first look to see where the sprinkler head is pointing, as you want the new one to point the same way. Sometimes you will have a small nipple attached to the sprinkler head. If that comes off also, that is ok.....basically just replace whatever comes off. These parts are cheap. You can also then cover the pipe so no dirt goes into the pipe.

Take whatever comes off and go to Ace Hardware and tell them you need this. Then just replace.

Now, dependent on weather this is a rotating head or just a pop up sprayer, you may need to adjust the new one so the correct spray pattern, rotation, etc so it matches the other one.

Frank