Answer to "How to access SIM card present under battery slot"The SIM card is used in conjunction with a WWAN card and a contract with a wireless provider that uses GSM/GPRS/HSPDA that's AT&T or T-mobile. Once you have the SIM card installed then you need to use the Dell Mobile Broadband card utilities to connect to the internet.
Answer to "Why is it recommended to install sd card when replacing logic board"I have replaced a lot of logic boards in MacBooks and I have never used an SD in any of them. All of the instructions I used from the internet never mentioned the use of an SD card when replacing the logic board.
Answer to "8 beeps with full black screen"The 8 beeps that you are receiving from the computer would indicate an issue with the LCD screen. I would suggest you to connect an external monitor with the system and press the Fn+F1 keys to us the external monitor. If the external monitor works then i would recommend running the LCD Built-in Diagnostics which the instructions can be found here - http://www.dell.com/support/article/us/e...