The 1750 analogy doesn't really fit, since we've already got a manual on using things (4th edition), and while things have changed greatly since then, it's only a few years' worth of difference. So in that analogy, we'd be 1750 AD people who were already explained how airplanes work, and then are faced with either a jet or a spacecraft, depending on how different things are.
Also, according to Sleepy Hollow, 1750s people can totally adjust in the present.