Sadly.... these will be two different issues in court. The judge will address them seperately. Your friend will have to pay back the money plus legal fees, and the buyer will most likely be fined for his harrassment and pay fees. If this is a matter of principle to the buyer, he will most likely carry it out just to prove a point and make your friend see the consequences of his actions.
The buyer bought a d-9 gun and that is exactly what he got, there are no refunds through email, he should have bought it while it was still listed on ebay. The only downside to this was my friend having to deal with a 40 year old maniac.