About the only thing I could recommend would be to take the glass off the top and clean it on both sides.  Outside of that, the little paper insert may need to be replaced.  If the key insert is a plastic-cardboard variety, there is not a whole lot you can do short of replacing it.  If you have a thirties or forties Underwood or Remington, go across the letters with a straight pin to remove the dirt.  After you do this, get some latex paint and smear it into the valleys of the letters.  If you have a fifties machine or later, with full plastic, all you can do is just clean the surface.  If it has that white junk on the surface, clean them with tranny fluid, as the keys have dried out.

What can I use to safety wipe/clean the keys? Also what tools are needed?

Is Lysol wipes okay just for disinfecting everything?