Hi,
You might have to do a little fiddling. First thing, make a duplicate of your project and work with the duplicate. That way you can move things around and experiment while still preserving your original project. To duplicate your project go to the project browser screen (where your projects are displayed as icons) and move your cursor over the title of your project. A little circle with dots in it will appear to the right of the title. Click on the circle and, from the pop up menu, click on Duplicate Project. A duplicate of your project will then appear in the projects browser view. Your original project will be preserved.
In the duplicate project, Instead of replacing the clip, you might try putting the new clip in the timeline above the old clip. Then the timeline would cutaway to, and play, the new clip in the place of the old clip. You wouldn't have to touch anything else in the timeline. The new clip would need to be adjusted to the same duration as the clip that it overlays. You could trim it or maybe vary its speed slightly, if that's possible without disturbing the flow.
You could also insert background clips or still images as spacers.
-- Rich