Dell Inspiron 15r N5010 LCD Black screen problem

I own a Dell Inspiron 15r N5010.

Few months back , I intermittently faced black screen issues. The laptop screen would go show black screen while playing games or during work. Now the laptop powers on, but there is no display.

A list of things that I have tried,

1. Connected to an external monitor. No display there as well

2. Reseated LCD cable. No hope here too

3. Removed RAM, tried a new RAM. No display

4. Removed battery, used charger to power on the laptop. No display on this step as well.

Now I am unable to even see the BIOS screen. I would like to know the below,

1. Can it be a motherboard issue. The approx cost of replacing this from DELL.

2. If it is a LCD lighting issue (I am suspecting this because, the screen behaves like laptop is powered off). The approx cost for replacing the LCD screen.

Thanks in advance.