I imagine it would be similar to what the Sith Emperor did on Nathema.
"But the ritual was not confined to the doomed Sith Lords. They were but the eye of the storm; the center of a vortex that spread across the entire planet. Every man, woman, and child on Nathema died that day. Every beast, bird, and fish; all the insects and plants; every living being touched by the Force was consumed. When the ritual ended, Nathema was no longer a world. It was a husk sucked dry. Lord Vitiate sacrificed millions, stealing their life force to make himself immortal. Their deaths also made him stronger than any Sith who had come before, and he ceased to be known as Lord Vitiate. On that day, the Emperor was truly born."
This is what was known as "The Void", where every living thing that was touched by the Force was dead. The planet was still there and accessible (It was later visited by The Exile and Revan) but the Force was simply not present.
As for if Kreia's plan would've worked? Kreia had the gift of foresight, as she was able to tell the destinies of The Exile and her companions at the end of the game, it's logical to believe that she saw what the universe would be like if her plan succeeded.