In order to change the default search engine or the order of search engines in the top right search box in Firefox, please perform the following steps:

1. Move the mouse cursor inside the search box at the top right of the Firefox window and click the down arrow next to the provider's logo.
2. If you would like to select another search engine, simply pick the engine from the dropdown list.

In order to change the order of the search engines, do this:

1. From the dropdown list, select Manage Search Engines....
2. In the upcoming window, you have all your search engines listed. To change the order, simply click one search engine and then select Move up or Move down from the buttons on the right side in order to change the order of the search engines.

I want to change the ADDRESS of Amazon.com as it is used in the search engine, not the order in which it appears in the search engine list.

You will have to edit the amazondotcom.xml file (or other search engine that you want to modify) in the searchplugins folder in the Firefox program folder to achieve this.
It is probably best to make a copy of the file and place it in the searchplugins folder in the Firefox Profile Folder.

You can use this button to go to the Firefox profile folder:

• Help > Troubleshooting Information > Profile Directory: Show Folder

If you do net have a searchplugins folder then you need to create this folder. In the case of the latter you will also have to change the name of of the search engine in the file I don't know which changes you need to make in your case, so you will have to figure this out yourself.

See also:

• http://kb.mozillazine.org/Using_keyword_searches
• http://kb.mozillazine.org/Location_Bar_search
• http://kb.mozillazine.org/Search_Bar

In order to remove the amazon.com from the search engines, do this:

   From the dropdown list, select Manage Search Engines.... 
   Select Amazon.com and click the Remove button