Polo
It depends on how confident you feel about opening up your camera and working on a sensor. If in any doubt then don't attempt it, I have seen quotes on the net for cleaning around £50 plus VAT and P/P.
If you want to try for yourself you need a cleaning kit something from this site may help but have a look at others as well
http://www.morco.uk.com/latest/camera_clean.htm.
I use the 6th item (Sensor Multi Pack with E2 Fluid ) in the list at £26.95 which gives the pads wipes cloth and fluid.
If you look around the internet their are videos on how to do it, there are numerous sites that show different methods and cleaning equipment. I would say google "cleaning camera sensors" and have a look at several videos first before you make a decision
However as others may mention it is a very delicate task and needs to be done with GREAT CARE and plenty of time, definately not to be rushed. Think of yourself as a surgeon performing an intricate operation because in effect thats what you are doing. It need 100% concentration without interruption, and a clean environment like a kitchen where dust won't come up from a carpet or off furniture.
Bazza