Susan -
reading about your experience just verifies for me that docs do things differently.
I had the hat like you - complete with smiley face stickers - but I didn't have to change my gauze at all; I was able to remove the "hat" and gauze and toss them 24 hours post op.
I also was able to shower - holding a cup over my BAHA site - once my hat was removed, so I was able to go back to work with clean hair.
I had the "dent" - which I like to refer to as a divot - for about a week to ten days, but eventually the area rises and the divot isn't as pronounced. In the end the abutment is actually very close to the skin. Numbness lasted a while, but at the time of my BAHA surgery, my head was still numb from my AN surgery.
One of my favorite things during the healing process was reaching up and running my fingertip over my abutment to hear the sound it would make; a very nice preview of positive things to come.
Jan