I have the same pesky oil spots as yours but I rather wet clean then send it in to Nikon. It literally takes about 4 passes w/ 1 sheet of pec pad cut into halves and wrapped over a swab w/ couple of drops of eclipse. Mind you I've never done a wet clean before owning the d600. I do this every other shoot and my sensor is spotless regardless of oil or dust. This is routine maintenance so I'm puzzled as to why other people are screaming bloody murder with a few specs of dust or oil. I know I will handle my camera with greater care than who knows what at the Nikon service center. Plus there won't be any chance they'll be sending back my $2000 camera w/ impact damage or just drop it off the front door without a signature request. If you still plan to send it off just be sure you document and date everything for your own peace of mind, just saying...Good luck and happy shooting!