Be careful of one thing. When you disconnect the key fob battery, the key will lose its synchronisation with the car. All you need to do a resynchronise is to open the door and put the key in the ignition hole. You should hear the steering lock work.
If the car is locked while you do this, the remote won't open the car until you have the key in the ignition, so you have to open the car with the metal key. Which will be difficult if the car is parked against a wall. The keyhole is only on the passenger door.
