The first thing to try is a hard reset. You can do this by holding the home and power buttons in until you get the power off slider up the top of the screen. After it has shutdown power it on again and see if it has fixed it.
If that fails then I would assume either the LCD or 6R8 coil is dead. Before you go ahead and replace anything I would first inspect the mainboard for corrosion and if you find any clean it with isopropyl alcohol.
If after a clean it's still not working then I would first replace the LCD and if that fails then take it to a repair store to have the coil replaced.
I hope this helps and best of luck with the repair.