Auto body repair & detailing: side mirror only replacement, sponge rubber, mirror glass

Question
My girlfriends mirror (glass part only) fell off.  I have a new one on the way but am concerned about what type of glue to use.  I don't want to damage the back of the mirror and it needs to stick to the plastic base (ABS I think).  Any suggestions on a quality glue that won't damage the mirror or the plastic, and will hold permenantely?

Answer
 colin

 clean off all old glue by scraping off.  apply windshield urethane adhesive to mounting pad areas press in place hold in place with sponge rubber  and rubber bands to keep pressure and position on for 24 hr  use sponge pieces around edge to center mirror.
bill