Just a few pointers.
Wayne mentioned using the "B" mode when doing the cleaning. I read that B should be avoided when cleaning the sensor because when you use B, there is current going around the sensor because it's in active mode, trying to catch light.
Second, when you use the auto-clean feature (on open and shut-down mode), it's better to put the camera down on a solid surface. Apparently ( some store technician told me) it helps the ultra sound to do it's job better.
But, really, don't wait until you see these at below f8 or 5.6. If you are not sure about how to do it, go into a store that does it for you "while you watch". then, gather the supplies and do it yourself. This is maintenance that you will have to learn sooner or later. And, as fas as I'm concerned, the sooner the better.