Ok looking at the instructable yes for the most part it will get you up and going.

There are a few differences from the 12" pdf(i still havent looked at the entire instructable)

I will say i didnt follow the video for setting up mine i followed the pdf. There were a couple things that were not covered in the pdf that were covered in the user manual from reprapelectro that i felt were important.

Like setting up the arduino board to be a rambo instea of a mega 2560

As to the heated bed, they're never flat they are too thin to ever truly be flat. Go to walmart and grab 1 or 2 twelve packs of small binder clips they are .88$ a box and use them generously to secure your heated bed to tour glass. Because the size or the bed is so large 4 clips will never hold thw heated bed to the glass and you want the glass to make the heated bed more rigid so that your leveling will actually make a difference.