Carol, The first thing you need to do is make sure you have set the Living? field to YES for any person who is living or maybe living.
You can check this with the View > Individual > List. There is a L for the heading. Check for U as others will be Y or N.
Next Search > Inividuals > Vital Statistics Living Search Y after all are found do a Grouping. Now go to Search > Grouping find Vital Statistics mark Invert Selected and click o Search. This will give you all of the non or unknown living persons.
Now use this List for your GEDCOM.
The other way to do this is after you have set all the living to Yes would be to use a third party program.