The difference between coaching and mentoring is essentially that coaching is non directive whereas with mentoring, the mentor imparts the wisdom of their experience.
A good definition for coaching is “a process that supports learning, development and performance improvement”. For mentoring read “the transfer of knowledge, wisdom and experience from one person to another”.
To be a successful mentor you have to have knowledge of the subject on which you are mentoring because a significant proportion of the role is to impart advice. Non directive coaching is more about asking questions and getting the coachee to soul search for their own answers so it's not as important for the coach to have deep inside knowledge about the subjects under discussion, more a background understanding of the environment in which the coachee is working. Having said that, there are professionals offering their mentoring services who may not have direct experience of their mentees roles. This may work and it may not, this is the area where you and only you can decide.
Peer Resources - A global leader in peer assistance, mentorship and coaching.
Encourage Mentors Professional Mentoring - Coaching and mentoring support for Interpersonal Communication, Self-Management, Stress-Management, Problem-Solving, Team Development, Decision-Making, Conflict Resolution, Performance-Management and Leadership practices.