Something I would like to do, however, merge overlapping polygons in gerbers. Is there any capability for that built into EasyGerb? Or do I need to use a separate program like Ace?

For features like overlapping polygons that would require ACE (as EasyGerb just simply converts selected objects to Gerber). ACE is a stand-alone tool that can easily convert DXF/DWG files to Gerber, plus it has a similar interface to EasyGerb (i.e. select layer options, etc.) for easy learning.

Here's an article I wrote about AutoCAD to Gerber conversions that you may find helpful.

http://www.numericalinnovations.com/pages/dxf-dwg-conversion-secrets-for-gerber-gds-ii-odb-etc

http://www.numericalinnovations.com/blogs/news/6116174-dxf-dwg-to-gerber-conversion-guidelines

Here's a forum post which may help:

https://numericalinnovations.freshdesk.com/support/discussions/topics/14000003213