How do I replace the lens (and black plastic framed backing) in my 2003 Oldsmobile Alero Penger Mirror.?

The lens and plastic its mounted on just fell out, and is lost. I have the same mirror which is not mountable, but the lens is good. I just cant figure out how to get it out of this old (otherwise broken) mirror. There is no way into the mirror except by removing this lens (and backing). Should I just try to pry it with the leverage of a screwdriver? There is a slot in the plactic frame that backs it.