My question is, does this mean I can only upgrade it with DDR3 1333MHz RAM cards?
Also, it says it supports up to 8GB, does that mean a total of 8GB? Or can each card only be up to 8GB, and a max total of 16GB?
And finally, how many pins does the RAM card need? 240 or other?
Officially, that Mac only supports 8 GB of memory (2x4 GB), but other sources have determined that the Early 2011 MacBook Pro supports 16 GB of memory (2x8 GB). Also, the memory must be 204-pin.
You can buy the RAM in OWC or Crucial (Crucial is cheaper and offers the same compatibility warranty as OWC)