Sarah - no question is ever silly; so ask away - never hesitate.
Brushing and/or combing my hair with a BAHA abutment in my skull isn't an issue for me. Only thing that sometimes occurs is that I hear a "click" when the comb or brush comes into contact with it. No pain, just a noise.
My BAHA site is directly over my AN surgery site (retrosigmoid approach) which is slightly above and behind my ear. The abutment hardly sticks out at all - I'd estimate there's only about 1/8" between it and my skull. BAHA sites also sink a little, so that helps.
The "device" (processor) is about the size of the first digit of your thumb - from the tip to the first knuckle. Here is a link that shows my processor (a Divino at the time).
http://www.anausa.org/smf/index.php?topic=6634.msg65388#msg65388When I wear my processor, it obviously sticks out a little - but it's nothing that my hair doesn't cover. I wear my hair fairly short - collar length - and it's never been an issue for me. If you were standing behind me and looking at my head, you'd be hard pressed to see it, even if you knew it was there. This is pretty much true for most women - our hair covers it. Men, who wear their hair short, usually have more noticeable processors. Processors come in different colors, which helps them blend in with your hair.
Good luck with your surgery tomorrow.
Jan