Had one replaced on an Audi, it was involved! Fortunately covered under warranty. The steering angle sensor provides important data to the stability/skid control. In order to counter an incipient skid or spin by individual braking of specific wheels (thus the need for the modern, 4-channel hydraulics on braking systems now), the stability control computer monitors input from the wheel speed sensors on each wheel, the steering angle sensor and perhaps other data about the instantaneous and continually changing status of the moving vehicle's relationship to the road. So it would not surprise me to hear that after replacing one of those critical sensors, the stability management system needed to be re-programmed. I've been driving for 65 years and LONG before "stability control" and "skid/spin management" were done by anything but the seat-of-the-pants skid sensor and the processor between the ears! However, these systems on modern cars have evolved to where they're better than 95% of drivers (all but veteran racing drivers maybe!) in terms of speed and accuracy of response. I think the car without them is certainly drivable, but not taking advantage of a very important safety feature. I think if at all possible, it's a fix I'd try to do!
