2005 xc70 Battery replacement:
Managed to get inside car and uncover battery compartment with no power (battery dead) by climbing through from back seat. Is it safe to remove bad battery so I can walk it across the street and get new one? What exactly is the removal procedure and reinstallation procedure? After reinstallation, what needs to be reset, and how do I do that?

 

Undo terminals (if battery has a charge, it's best to remove the negative first - to prevent possibly shorting your removal tool between the positive and the body and same safety precautions going back in with a new battery. Connect the positive first and negative last - again to prevent possibly shorting your tool between the positive and the body with the negative connected.

Nothing needs to be reset on a 2005, later cars have a battery management system that should be reset.