I can attest from personal experience (sitting in an old Holden under the UQ Electrical Engineering department's High Voltage equipment for a discharge of a few hundred thousand volts) that being inside a car is perfectly safe, as long as you don't touch any of the metal work (door handles etc), as the car's body makes an excellence protective Faraday Cage.
As for the electrical equipment - it may or may not suffer any damage. I'm not sure whether disconnecting the battery would have any effect though - the induced surge currents are probably totally independent of whether the battery is connected or not. In the UQ's Holden, part of the demonstration was that the radio still worked after the shock, but electronics gear was a lot more "robust" in those days. Modern solid-state electronics can get fried with just a few volts / milliamps in the wrong place (which is why you need to wear an anti-static grounding strap when working on sensitive electronic gear).
http://www.lightningsafety.com/nlsi_...le_strike.html