Is it possible to import/export map data (or backup) other than importing the database tables? I tried to check the documentation, but it currently turns up a 404: web-dorado.com/wordpress-google-maps-plugin/installing.html

Hello Aaron!

Please note, that you can export Map Markers, Rectangles, Squares, etc using Export button, and Import them to your second website.

Also, in case you have Pro version and got the themes, you can copy your map theme code and paste it in the themes of your second site, after unchecking Auto Generate Map Style Code option. These can be found under Google Maps WD > Themes area.

As for your note about the 404 error, this problem is already resolved, please access the guide using this link instead:
web-dorado.com/wordpress-google-maps/installing.html

Thank you!