The D7000 seems prone to gathering "STUFF". I have had it cleaned 2 times now with something on the sensor that could not be blown of with a rocket blower. Wondering if it is lubricant or something.
I seem to have to clean it more often than i have ever had to do with my D80, D90 or D300s.
I say let a professional do it. The Certified Nikon Repair facility (conveniently 15 minutes form home) does it while you wait and they use a big static controlled booth contraption that has a microscope on it. So when they are done, it is perfect. They shoot a before and after shot for me. Although I always check it myself.
Easiest way is to shoot a white piece of paper with a flash from 2 or 3 feet away at F32 or higher. I use a semigloss photo paper which is slightly reflective.
If there is something there you will see it! If it is minor and the blower will not remove it then a fine sable hair paint brush may be used to dislodge it. Ever so gently of course. beyond that I let the pro's handle it.
Messed up a focus screen on my D300s trying to get a little more aggressive on my own. Had to take it to the pro's to replace and get clean.
I am sort of anal about it being perfectly clean and spotless. The slightest spot makes my blood pressure go up.