To start off - I'm not a pro either. And I also was frustrated with my D90 back focusing issue. Which only sped up my upgrade to a FF camera, which was D800.
I got my D800 early on and am now dealing with focus issue. Since this is a lot of money, if you do decide to go with either model of D800 I would strongly suggest buying it from a dealer who has good return policy (no questions for a month?). Also I would highly suggest buying and then returning (sure, it's bad) if you don't want to keep a good fast wide lens (24mm? 35mm?) - which would allow you do to focus precision testing. If you do notice bad/inconsistent focus, do not hesitate to return/exchange camera right away. Do not bother sending it in for service.
And good luck to you no matter what camera you choose!