It's too complicated and far too long to be a starter series if you've never read any Fantasy before. I started WoT also back in the 90ies, but before that I've already been a reader of Fantasy for ten years or so. In fact, ancient myths and sagas got me into reading Fantasy. Myths and sagas...
If the actor even does not play, letting him have a guitar is even more, well, idiotic. Probably they'd better casted musicians instead of actors, especially harpists.
Correct strings: Because one sees the difference.
What about the harp and flute from the books? It's quite obviously no modern concert harp, there are many examples throughout history for smaller and transportable harps. :desk Also a mandolin or lute would have been far more fitting for a former court bard than a guitar if you needed to differ...