I have a sliding glass door and the glass is etched around side; the seal broke and dust has come in and I don't know how to fix it.
If repairing the glass as RQDQ suggests does not pan out, you have three options:
In either of the last two cases, it is more than a 1-person job; be sure to have help to safely handle the removal and replacement of the panel or door unit.
Is the glass etched or cracked? If it's etched (and you can get to it), you can polish that out. The seal broken is a different issue. There are kits available on the market to remove moisture and replace the air between the panes with an inert gas.
Depending on the age of the unit, it might not be worth repairing if it's on the verge of failing in other areas.
This page discusses some options for repairing windows: http://homerenovations.about.com/od/windowsanddoors/a/artfailedwindow.htm