Very good work for a 1st, with regards to the eyes this method should be fairly simple to explain. Export your model at a fairly low subdivision level from zbrush as an obj. Import this into maya and create a sphere for the eye. Put this in the correct place and then duplicate or mirror this over to the other side and export the eyes only as an obj.

Now load your demon up into zbrush and go to the poly sphere tool. Now import and browse to your eyes obj. once loaded go back to your demon tool and on the side menu you should see an attribute for sub tool. Open this up and select append and you should have your eyes option in here.

They may be invisible on one side in which case you need to go to display properties and click on double.

Hope this helps and keep up the good work.