If you were unlucky enough to have a failed autopilot I think its very unlikely there would be a successful outcome with a basic PPL of hand flying a commercial airline from say FL380 to a successful landing.
it Is not just about the skills required which are very different to flying a single engine piston but also about not becoming overloaded and loosing control from the situation itself and complexity and differences in the aircraft.
If you had the autopilot and someone was guiding you through what buttons to push then the PPL would give you a basic understanding which a non Pilot would not have.
thats my opinion but would be interested in what the heavy iron pilots here think
Even with my bottom of the pile business jet i do not think there would be a successful outcome to a landing from FL380 hand flown by a basic PPL and that is even presuming the weather condition were good
The biggest problems would be speed control, altitude control and profile control which would lead to overload and loss of control and we haven't even got to landing
Pace