For (2) I normal have to worry only for the UV filter that protects the lens and the rear element. Both I use a good blower to blow dust away. For the filter, I (but seldom) use a micro-fibre cloth to wipe away stains and fingerprints (hate those the most).
For (3), just a normal clean micro-fibre cloth to wipe it. If after a near-the-sea/beach shoot, I'd go for a mildly moist cloth to wipe it gently.
I do not believe in going way overboard as my camera gear is for use, not for collection. And even then, I daresay that I do take quite good care of my gear.
External cam body cleaning shouldn't be a problem, when it comes to the CCD sensor better to let Canon Service Center do it. You wouldn't wanna touch those if you aren't experienced, any wrong move could be costly Not sure for Canon, but I know the cleaning service is free for Nikon when under warrenty.