One change...we never saw Chekov until later on in TOS. But that could easily be explained as books or EU are not canon, only really onscreen is...he could have been on the enterprise, assigned elsewhere than tried to get reassigned back on.
We already know that Chekov had been on the Enterprise before we actually saw him, otherwise he wouldn't have met Khan in "Space Seed" ...

My real problem with Chekov in XI is that he is supposed to be a lot younger than the rest of the main TOS crew. There is no way he would be serving under Pike as a bridge officer while Kirk is still a Cadet!