Where is the phone's backlight?

Hi,

After water damage and drying it out, iPhone finally came on but the tochscreen is not working at all.. can´t slide the bar to get into the phone, can´t turn it off... etc... also it does not have a backlight... i can see the phone is on but very dimmed..sound, it rings, but can´t answer calls and no backlight.

I am about to purchase the parts to fix this but would like to know if i just need the front glass + digitizer alone or should i also buy the lcd screen to fix the entire problem...

Thanks a lot in advance...