Userscripts.org

To edit a userscript:

1.
From the menu, select Tools → Manage User Scripts.... Greasemonkey will pop up the “Manage User Scripts” dialog.
2.
In the left-hand pane, select Hello World and click Edit. This should open the installed version of Hello World in your favorite text editor. (If it doesn't, verify that .js files are associated with your favorite text editor.)
3. Ctrl-f to find "var newLogoURL =" (minus the " " marks). Replace the URL provided by the script with the image URL of your choice. Do the same for "var newSearchURL="
4. Save your changes in your editor, then go back to your browser and test the change by refreshing any page. You should see the results of your change immediately; there is no need to re-install or “refresh” your user script in any way.

(Directions modified from http://diveintogreasemonkey.org/helloworld/edit...)

I updated and corrected some of the script, so it should work now. Let me know if still doesn't work.

The link is "google.tld" so that it will work on all Google sites, regardless of nationality.