I've been following this whole D600 dust/oil issue and it seems people are divided into two camps.
The first camp, to which I belong, has decided to wait it out until Nikon comes out with a statement declaring that the issue has been resolved starting with serial # ------, or reports of dust/oil by users die out because Nikon secretly fixed the problem.
The second camp says just go ahead and get the camera, do the cleaning yourself or send it to Nikon for cleaning.
My problem with the latter approach is
(a) There is always some risk in cleaning any optics. If your brush happens to drag a hard particle across the sensor (actually the filter) it could result in a scratch and make matters worse.
(b) My experience with Nikon service has been, shall we be generous and say, less than satisfactory. I'd be afraid that I'd send them my D600 and get a lens cap back.