I get that the point is to be simple, So I will not complain about the lack of complexity, But you could have made it even simpler (And better) by changing the dialogue tree based on the progress in the quest. This would nullify the start quest script, And it would make the whole thing look better.
All you would need to do is add a hashistory node near the beginning of the dialogue box. It is easier, Simpler, And much more attractive that way.
I would like to see a series from you on advanced scripting. Like, Real advanced scripting. Using vars and vectors and dynamic stuff.