There are several ways to get the result you want.
Probably you should develop a so called “widget” that opens up if any defined key is pressed. You should find several tutorials about that 
I myself learned everything that way the last months.
In the Widget you script any action that happens to the mesh if you click on the menu. I didn’t try it yet, but the Textures to show-up should be just the “getMaterial” or sth and after you click on a button it changes, hope that helps.
If you haven’t got any idea about blueprints thogh, you should start with some simpler things (for example move a box on the Z-Axis when you leftclick, whereever you are)