You can inherit component properties by using sling:resourceSuperType property.
In this example we will override image component.
After creating the component, delete .jsp file created under the node. Add the component to the page. This is how the dialog would appear. This dialog is inherited from the image component.
Now, let's say you need to change text of first check box. To do so you need to recreate dialog structure till that checkbox field (You can keep all the created nodes empty and of type nt:unstructured.). To override text of the checkbox add highlighted property.
There you go! We have successfully changed the text.
In AEM the default functionality is available in "/libs". Overlaying means copying the functionality from "/libs" to "/apps" at exact same path. You can do the desired changes in newly copied functionality under "/apps"
AEM uses search path to find a resource. As per the default OSGI preferences(set in Apache Sling Resource Resolver Configuration), it first searches under /apps and then /libs, so your newly copied component will get priority.
As we are aware, following screen is a predefined functionality by AEM and thus it resides inside libs(Specifically, at /libs/cq/core/content/nav).