Replace rear mirror for auto dimming
 

I am planning to replace the rear mirror with an auto dimming one on my recently purchased 2004 S60 2.5T. I have found a few on ebay. Is there any particular thing I need to pay attention to when disconnecting the old mirror and reconnecting the new one? For example should I disconnect the battery before doing the swap so as no error message appears later. I am asking because when I replaced my radio with an aftermarket one that triggered the air bag message to display. I learnt later that I should have disconnected the battery before working on the radio.
Thanks
Alain