If a carotid artery is occluded (completely blocked), nothing can be done surgically to unblock it. It is simply too risky because the blockage cannot be pinpointed with an angiogram. In your case the left side will sufficiently supply the brain with blood so take care of it.
Yes, they can operate and correct the problem and this is done pretty routinely now.
this happened to my father at 72yrs old, on both sides his corroted arteries were almost completely blocked on both sides, he was operated on and they were cleared. If left they can cause serious problems, Sometimes they can be partially blocked and medication is enough to thin the blood so it gets through.to the brain. His tests should reveal the prognosis. Good luck.