Use a spudger to gently pry up the end of the logic board closest to the dock connector.

There is a small golden grounding tab on logic board adjacent to the 'do not remove sticker'. Be VERY careful this does not snag on the side of the case when prying up the logic board; it breaks easily. If you have signal problems after removing the logic board, check this ground tab.

If the board won't lift up, double check to make sure all the screws securing the logic board have been removed.