Failed Firmware update mid 2012 retina macbook pro

I think I have a failed firmware update as my dedicated graphic card is only working occasionally after an interrupted firmware update. I cannot boot into windows and to boot into osx I need to sleep the computer (shut the lid) and the n wake it up and it will do a screen flash and then work, but the NVidia 650m will not show up in system profilier. How can I do a firmware restoration for this laptop?