i took my v70 to the dealer. there is a computer (chip) or something in the interior rear view mirror. were is the best place to find a deal on this part and how do you know what to look for?

2002, v70
my gas lid button stopped working, so i disconected the ground off the battery. 30 seconds later i reconnected the ground wire. now my sunroof, interior lights, keyfobs and visor mirror lights dont work. what did i do wrong and how can i fix it