You are not actually cleaning the sensor but the protective layer above it. While I am very happy to clean my "sensor" and cannot see what could go wrong with this simple process which takes only a couple of minutes, I would not wish to encourage anyone to do so if they do not feel confident.
Have a look at the video below which shows just how easy it is though I would not recommend that you clean your sensor in a car park.
Strobist: Sensor Cleaning Demo