You can switch providers in Firefox by clicking the search icon next to the address bar and selecting the engine of your choice. You can also do this to re-select Google as your primary search engine after the Yahoo Search switch rolls out.
But if you're not interested in trying something new and can't be bothered with messing around with the Firefox defaults, Google searches will still be easy do in Firefox even after the change. Along with the new search provider, Firefox is rolling out an improved search interface that will let you get results from Google or any other installed search provider on Firefox with just one click.
Sign up for CIO Asia eNewsletters.