At the mo - the only way I can think of having a NPC 'help' you, is having an NPC as a medic - having him stationary or follow waypoints to a predetermined area - perhaps having the NPC talking (sound recording) or text on screen, and then have a heal zone (perhaps with some medical equipment as entities in the same place?).
It would look like the NPC had taken you somewhere to heal you.
NPC's could also give you clues as to where to go - what to do, via sound recordings or again, text on screen.
I think (I iterate think) benjamin A did a tutorial on talking NPC's with text on screen? Hmmmm can't just remember.
Its pretty darn good.
Try a search dude.
Hope some of this helped in some way!
Mabuggi.
DAB Studios