I like the second image for the line style.
Shading is a bit confusing though, the dark for the inside of the bigger object is good, but on the ears you have the shading on the outside.
Using white for the printed side and dark for the unprinted side does look really nice.
I always assume people don't print the instructions, most people work near or at their computer, so ink costs don't really come into it. You could always do a whitened grey shading, but I like what you have done.
Been trying to do instructions in a similar style of showing the cut lines, but without the thick outline.
(it'll look better with numbering)