Yeah, that can be done.
Go to Geodirectory >>> Settings >>> select post type (tab on top of the page).
Now select 'edit' below gd-place.
Once clicked you see the page where you can change the names. First (top right) click "show advanced". Now you see all fields you need, and everywhere it says 'place' or 'places you can set whatever you want. Tip: pay attention to single and plural.
