Is it possible to replace the headlight switch without taking the whole dash apart?

This will depend on the year...if you have one of the earlier cars with a "conventionally" styled dash, you'll have to take the dash or parts of it off. If you have one of the newer ones with the knob sticking out the side of the gauge cluster, you can pull the controls out of the dash. Grasp the entire switch (both the selector knob and the labeled part) with your hand, and slowly but firmly pull it away from the dash. It may make a cracking noise while doing this, but this is the switch clips and not anything you need to worry about. Once it comes out, there will be a wire harness connected to it...pull enough of this out so it does not fall back into the dash, and disconnect the switch from it. PLEASE BE CAREFUL, THIS CIRCUIT STILL CARRIES POWER WHEN THE KEY IS OFF. Then, connect the new switch and pop it back into the hole...it should fit nice and tight, but if it is a little loose you may want to consider a small amount of hot glue behind the switch to hold it in. Hope this helps.