Would someone who is not a professional but knows a subject (such as automotive repair) in depth and offers advice and hands-on assistance with repair procedures be considered a mentor? Is the act of giving advice in this context mentoring?
Mentoring refers to the passing on of knowledge and expertise over a long period.
The mentor might be a professional, but they also might not. Likewise the relationship between the mentor and the protégé might be within a professional context, but again it might not.
The skill the training is in might not even be one that is ever professional; people often mentor in hobbies, sports and other avocations that don't have a professional structure.