Hi,
An 8 beep error code in your model indicates that there is a problem with the LCD.
It may be either the video flex cable between the motherboard and the LCD screen or the LCD screen itself.
Here is a link to the service manual for your laptop.
http://downloads.dell.com/manuals/all-pr...
Click on the Display link in the contents page to go the the display section of the manual. Here it describes the necessary pre-requisites and the procedure to remove the LCD display. Use the guide to first re-seat the LCD cable ( i.e. disconnect the cable from the motherboard and from the LCD screen itself and then reconnect it, and then re assemble the laptop to see if the problem has been fixed.
If it hasn't been fixed you will have to replace the LCD screen
.