On the surface it doesn't seem so hard. Most of the effort can be concentrated on one hand and one foot. Throw a manual transmission at it, and most of the effort can be handled by one hand, and two feet... most of the time.
Shifting becomes a bit tricky. It can only be done on straight roads, or when nobody is driving next to you. If I was driving a diesel it would be made worse as the rpm range on a diesel is so narrow. As it is, I can leave the car in gear longer that I originally would have intended without significant impact to the car or my ability to drive it.
I'm not sure if it's wise to be driving my car with only one functional shoulder. I don't think it's illegal... although if it is would somebody let me know so I can stop doing it before I get a ticket?
Perhaps the best idea is to limit to driving to be on an as needed basis to reduce the chances of getting into a situation where I need to shift and steer at the same time.