I'm terribly sorry if this is a super newbie question, but alas, I've only had my camera for about a year, (Digital Rebel XT, 8mp). When should I start thinking about cleaning the sensor? And is it a good idea to get it professionally done, especially if I'm unsure of what I'm doing? ... I saved for an entire summer to buy my camera, I would rather poke myself in the eye with a rusty nail than hurt my baby...