My method of getting a D800 is the same as all my equipment, in person, trying it out and dealing with a reputable pro shop.
Nikon funneled most D800's through locally owned small shops, having learned from the D7000 high return rates of fully functioning cameras from on-line stores. As it turned out, most of the initial problems were user error or lack of understanding the fundamentals. As the same people got more experience with it, magically the camera healed itself. Having an informed shop owner as your salesperson should short circuit some of the potential complaints. It also allowed the only opportunity for someone to suggest a more appropriate camera for the buyer if it was overkill. A great many people who bought D800's(and D7000) were upgrading from much less demanding cameras or point and shoot.
At the very least, getting it from a good pro shop would allow you to try it and verify to yourself that you are getting a correctly focusing unit.
The D800 is not a camera to get into unless one is prepared to invest significantly in the lenses and tripods that are suitable for it. If it is a strain to buy, as it would have been for me if I did not already have a collection of quality lenses, you really ought to rethink whether you are going to get the full value out of it when needing to cut corners on required accessories. A D600 is a very good alternative that would allow getting another lens suitable for it. A D7000 is the best in DX if you already have quality DX lenses. Unless you regularly print very large, few people would see the difference between properly exposed images, viewed at normal viewing distances, from any of the current cameras.