[JDFlint]

I searched for anyone else with this problem and it doesn't appear that any are the same.

My trackball has stopped clicking. When you go to push it down, it doesn't move down at all or click but still responds like it was. So when I hit down on an icon it will still select it.

Now I found this, 2 X New Blackberry Replacement Universal Trackball Dome Button Blackberry Accessories - Everything4Blackberry.com
How hard is it to replace this?

[aznlgcy]

Which Blackberry model are you replacing the trackball for?

I had a similar issue before and ust replaced it instead of attempting to fix it

[JDFlint]

A VZW 8130. I already replaced the trackball in it and it still doesn't click down.

[aznlgcy]

Then your problem is not the trackball seems like the sensor on the main board that is right behind the trackball. Don't think you can fix that

[shfjcs]

I searched for anyone else with this problem and it doesn't appear that any are the same.

My trackball has stopped clicking. When you go to push it down, it doesn't move down at all or click but still responds like it was. So when I hit down on an icon it will still select it.

Now I found this, 2 X New Blackberry Replacement Universal Trackball Dome Button Blackberry Accessories - Everything4Blackberry.com
How hard is it to replace this?

Your trackball dome is just tired and worn out, but apparently still functioning - amazing!

I don't know if your link is the correct part, looks like it is but not sure. I have replaced these before:
Cúpula perla de navegación OEM para BlackBerry - - Cellular Accessories | Mobile Accessories |

After you remove the retaining ring and trackball, get a pin or needle and carefully get under the adhesive around the dome and lift it up and out. Use a pencil eraser to clean the surface under the dome (if necessary) and simply replace the dome. It will feel like a brand new phone!

Hope this helped.