SSM members are notoriously reliable. I wouldn't worry. I've had numerous transactions with them as both a buyer and seller. I've never been disappointed.
I am very surprised tha tthe seller isn't asking for payment in advance... I would.
I always use PayPal, though and pay via Credit Card and that way if PayPal screws me if I have a claim (which ultimately they will) I can always dipute it with my Credit Card company.
"Never mind...it's just easier to call you stupid." -Brian Griffin