Hi Viken, Sensor cleaning is not difficult to do at all. I use the Copper Hill system and I found it to work well. Not sure whether it's the best - there are other systems/products as well. Copper Hill has a video on their website that shows the process. Cleaning the sensor on your D300 ought to be a snap. You may also want to read Thom Hogan's notes on sensor cleaning...hopefully others will join in for more advice.