I can talk about how people can scam with wester union since I have been through it. I went to a McDonalds one night and got me some food. I used my debit card as I do with 99% of the stuff that I purchase. The kid that took it sorta had it for longer then he should have, but at the time I didn't think anything about it. Well not but about 2 days later I get a call from my debit card company asking me if I sent $500 via western union to someone in AZ, I'm in KS, I said no, and they said that I had or that someone had with my debit card.
What the person did was sent money ($500) via the internet via my card and someone in AZ went to the western union location in and picked up the cash. I took the the proper steps to prove it wasn't me and the money was finally returned to me. So plan and simple that is how someone can scam with western union. They will send the money via the net with a stole card number, the seller will pick up the fraudulent cash and send their MBP, then when the money is found to fraudulent they will come back and get the money from the MBP sender and the scammer will get the MBP sent to some false address and walk away with it. easy as pie.
Don't do it. Sell it to a verified paypal member with a signature required! That way you are cover by paypal if anything happens.