Well, the colour change (blk to white) is pretty good, but then you used the clone stamp in an unappropriate place.
See that little line that you have right above your car? try using a closer clone next time (meaning that you should set the target to about 10 pixels above the part you're trying to clone.
Also, nice try with the front bumper, but the cut isn't clean. The part from the BM can still be recogized when you put the whole new front part on. Either try cloning it away or blurring it. Personally, I would clone it because blur rarely works for me.