My sensor became really dirty a month or two back, so I had to resort to cleaning it for the first time. I tried a decent air blower first, but that didn't remove the worst contamination, so I bought some Visible Dust swabs and cleaning fluid to match my sensor size. While I was pretty nervous about the thought of damaging my camera, I researched the process on Youtube until I felt confident in what I needed to do, and the whole process went smoothly and the offending marks were removed from the sensor. I certainly won't be particularly nervous the next time I have to do it.