Hacking NINTENDO DS REPLACEMENT BOTTOM SCREEN

[wiimii]

ok so i got a old ds phat and the touch screen is scratched to hell and i want a new screen butif i buy this ds, is there a cover that goes over the top of the ds touch screen like on the outer case or is the screen all one part ,sorry new to ds, but i have a couple of triwings left from opening my wii to install wiikey

thanks in advance