Have it done professionally. If your screen is interchageable you can remove it an use canned air to blow off dust. I've used very low pressure air to blow dust from the screen and mirror. These are the most sensitive surfaces in your camera and it's best to leave them alone as much as possible.
I have a friend who works in a camera shop that has an on-site repair facility. The repair technician uses a clean cotton swab moistened with acetone to clean reflex mirrors. The key to cleaning the mirror successfully is to not get the swab too wet so the acetone won't run into the mounting plate, and use very light pressure. I've used this technique a few times without adversely affecting the mirror. Remember to blow off any dust first with a squeeze bulb (not compressed air) so dust particles will not act as an abrasive. A true ground glass (the key word here is GLASS), can also be cleaned with acetone. However, if the focusing screen is plastic, acetone could damage it. I don't know what the screen in an N/F80 is made of, so I would use extreme caution here--either limiting cleaning to a squeeze bulb or a repair technician. I have never had to use more than a light puff of air now and then to clean the focusing screen, since it is not as prone to collecting crud in the roof of the mirror box.
I'm not sure what the ground 'glass' is made of either. I beleive it's glass as the mirror is. But I cleaned it again last night. With a que-tip and some alcohol. And I do use compressed air. And yes, the tip is to get 99% of the alcohol off of the que-tip before applying it to the ground glass. Then you must apply it evenly with almost zero pressure. Don't sweat the few strands of hair from the que tip on the glass, you can blow them off later. Just try not to touch the walls of the box cause they are a kind of felt material. And the que-tip loves sticking to the felt.
Everything went well. You can tell if you messed up because you'll have destroyed either the glass or the mirror. Basically, there will be a spot that you cannot get clean.
But I did it in last resort verses taking the body back to have it replaced. That's the benefit of knowing the manager of a local proshop.
The ground glass is plastic. In fact, I think my F100's ground glass is plastic. The grain is a sort of decal on the prism side of the ground glass.
I would seriously caution using any cnctact on the ground-glass... Once you nik one of those lines from the fresnel lens, you better be prepared to shell out for a new ground glass or live with a "visual deadspot" in the finder.
Also keep your soft brush free from contamination, especially from body oils it may pick up from your fingers or when you're dusting off you camera body and eyepiece. I keep one brush in my bag for less critical purposes and general dusting, and have one that's reserved exclusively for sensitive surfaces.