i use a skin from decalgirl.com to protect my ds
and a hori screen protector (i did buy a cheap one which was rubbish so bought hori)
try to put the screen protector under the skin on top screen, works out so perfect you cant see the seams
oh try to avoid dusty room and fans when installing screen protector and skin, says repositionable but i really have to disagree with that
i do get dirt stuck in between the cracks of the ds along the edge but i use a folded peice of paper or just open the thing up and clean it