It rather depends what you mean by "mockups." If they are purely graphics (with no underlying controls) then you cannot learn the GUI. If they are reasonable representations of the final GUI (with live controls) then you can at least build GUI files.
The mockups are actual GUI Screens with buttons and links but they are not connected to any databases (no live controls). If I automate using just the GUI screens will i be spending lots of time in doing rework when its actually connected to the live controls.
On the face of it, you should be good to go. But I'm not sure what you mean by "live controls." If they are REAL controls, but the underlying logic is absent, that's fine. The easiest way to find out is see what you come up with when WR learns the whole window of a mockup.