rearview mirror came off windshield. What now?
 

I was reaching over and my elbow banked into the rear view mirror on my 545i. Meaning the whole thing came off, the arm that's attached to the windshield came off.

I have the auto dimming, automatic rain sensor, and homelink if that matters. There's a module box attached to the windshield and a little sensor below it.

Is there any way to repair this myself or do I have to get a new windshield with attachments?

Can be glued back. You can get proper glue in auto store parts or stop by auto glass shop and ask to have it done. Not difficult repair.

Exactly, go to a glass installer they will do a better job with much stronger adhesive than you will be able to get.