Its likely something that has hardened and dried, pretty common actually.
Since you don't feel confident about doing it yourself, send it into Canon Mississauga. I wet clean my sensors whenever matter is actually dried onto them. The issue is not really electrical contacts, alcohol will not short the very low voltage contacts out. Rather, its the AA filter that sits on top of the sensor, and is not sealed to the sensor, so a excess of fluid can run under the AA filter and leave stains where you cannot get to them to clean it, removing the AA filter for cleaning the sensor would be very expensive, Canon won't do it.
If you purchase pre-moistened cleaning swabs, then there is no problem with excess moisture, but unless its something you do frequently, its very expensive, and it still might come clean. I buy my cleaning swabs and eclipse solution from micro tools, I already had a inspection microscope. http://www.micro-tools.com/store/SearchByCategory.aspx?CategoryCode=6