iPod Touch 2G broken screen
I haven't seen them sold separately. I imagine it is possible, but good luck finding one or the other by itself.

You can get the "front panel" assembly here ($70), which includes: touchscreen glass, integrated digitizer, metal frame and home button. Install directions here.

The front glass and digitizer should fix the touchscreen problems, but you probably will need a new display to fix the backlight (I haven't seen the light sold separate from the display). You can get that here ($60), with install directions here.

Hope this helps.