Sounds a bit like Arthur Daley speak.
Who told you this and why wasn't he more specific? Did he wear a sheepskin jacket, trilby and smoke a cigar?
Is the roof leaking? If not i'd leave it. It's doing it's job even if it may look scruffy.
Overhaul could mean anything from replacing a few loose tiles, doing some repointing, renewing flashings or complete strip and retile. From �100 up to thousands. Then you can start looking at the condition of the roof timbers!