Nav has nothing to do with the auto-dim mirror. It just needs the right mount or adapter to install in place of the standard mirror, and two connections for accessory power and ground. I installed one on my non-nav EX.
IIRC the glue to attach the mount to the windshield is special and available in any auto parts place. Last time I used it, you had to wait a while for it to cure before mounting the mirror. That glue is designed so that in an accident, the mirror "breaks away" without breaking the glass.