Upload & Sell: Off
Whatever gear you send to Nikon to repair, they always check everything. I had my D4 in recently as the viewfinder shutter was sticking in the closed postion. When it came back, they had adjusted the AF (my micro adjust AF settings were no longer accurate). They also update firmware and I know that there are more tweaks in the firmware revisions than they admit to. There are cases were the firmware number stays the same, but the "shop" version has fixes the public version doesn't.
As a routine, they check all functions and adjust as needed and do a very nice job cleaning the exterior. They will often clean the sensor, but my experience has been hit or miss with that. I can do that myself, so it's no deal breaker either way.