I don't have a D70 so I can't answer the specifics of how to clean that one, but on my Fuji there is a way to lock the mirror up and open the shutter without energizing the sensor. Basically the same as "B" shutter speed but without energizing the sensor. It needs to be done this way because when the sensor is energized it will attract dust. I use a blower bulb (not canned air) and haven't had any problems. I also bought sensor swabs but never got the nerve (or need) to use them. If that fails, try this link:

http://www.nikonusa.com/template.php...to=inc_service