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.

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.

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...