Adjustment to existing .stl file box

I have 2 .stl files (a box and a lid). I need the box adjusted: removing the clip system attachment of box to lid, one wall and divot on top, adding a different way to open and close box (see pictures below) I also need the box to be 5 mm wider and 5 mm deeper in the interior. The part that you grasp to open should be about 25 mm. Please only reply if you have experience making .stl files that are printable on a 3D Printer.