8 beep sound

Hi,
Am having Dell Inspiron N5010 i5 laptop. When I am switching it on , it is showing black screen and 8 beep sound. I tried connecting to external monitor but there also black screen. I gave the laptop to service centre , they kept it for onr day and next day they told me that the issue is with graphic chip and were asking for Rs 4000 for chip replacement. I denied replacing the chip and took my laptop back and surprisingly it was working fine with no issues.I used it for around 5 hours and it was working fine. But the next day again same issue i.e. black screen with 8 beep sound.
Someone plz guide me what is the issue and what to do ?
Should I give the laptop to the above mentioned service centre and get graphic chip replaced for Rs 4000. ?

Regards
Ankit