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If you want results that at least as good, or better, than what you got from a D700, then no, it's no harder to shoot at all. If you're going to downsample from 36MP down to 20MP or 16MP so you can get richer color information and a better 16MP file, then no, there's no additional challenge to the D800 at all.
But yes, you may need to change habits, improve technique, or do something else, if what you want is to get the best possible results out of that 36MP sensor with small pixels so you can make a very large print out of it.
There is no universal "right answer".