Thank you VERY much for your time!!! It works now! I truly appreciate it.

Do I have to select the whole Polygon shape in order to duplicate? Since it's still not working, urg...

(PS I'm working on Maya 8.5)
I'm trying to model half of a head and decided to duplicate it on the opposite side to make it whole. I went to Edit>Duplicate Special (options), set the X scale to -1...