Cleaning the digital sensor
The sensor cleaning digital SLR sooner or later is a necessity, since the changing objectives - whatever precautions you take - leading to the entrance of dust, pollen and particles in the space of the mirror reflex.
The operation itself requires some attention, but it is not a dramatic event. In fact, the maximum damage that you may cause to a sensor cleaning may be careful not scratch the protective glass that covers it, but it is a hypothesis rather remote.
Cleaning is normally done by the good photo shops, at a cost of about 30 euros. Or it can be done by specialized laboratories to do with time and higher costs. Or, it can perform on its own. To be fair, as some camera manufacturers recommend, in case of doubt on their manual skills is good to be cleaned by an authorized service center.
The need to clean the sensor is demonstrated by the presence of "spots" in the images, systematically positioned in the same places between shots and the other.