Thanks for the information.
I need to replace the rear view mirror. How do I remove the OEM base to allow for attachmemt of the new mirror?

It's held on by a double sided 3M adhesive pad if it's done the original way. Simply working a razor blade under the mirror (very carefully) should release it from the glass. Be sure to measure the distance from the top of the windshield for reattachment purposes before you remove it. Alternately, you can outline the position on the outside of the glass with masking tape before removing the mirror.

The trick I've found for reattaching it is to use two pads when you're remounting the mirror.