How do I insulate around a gas fireplace without tearing it apart?
Without a picture of your fireplace, I couldn't tell for sure, but I would look in to fire brick. It is a near perfect insulator since it is a light brick with lots of air bubbles (air insulates).

Check here:

http://www.google.com/products?q=fire+brick&amp;um=1&amp;ie=UTF-8&amp;ei=8n1YTJmlCd6Knwf7hZS2BA&amp;sa=X&amp;oi=product_result_group&amp;ct=title&amp;resnum=1&amp;ved=0CDIQrQQwAA

..or at a local fireplace store.