Whoa whoa....you have to send them back first? So Paypal said that as long as you ship them back first then they will pay you? How do they know the funds are available to them to repay you? Do they have it in escrow right now, awaiting shipping and delivery confirmation?
When it comes to this much money, Id want to know, that in the end, Im not out the item AND the money....
PROTECT YOURSELF!
Package them up as if they are in good condition. Take many pictures of how they are packed (make sure to put a date in the pics, too)!
Bubble wrap everything, seal everything. Use a new box, too.
INSURE THE PACKAGE! For cripes sake, insure it for what they are worth to replace.
Whoever you send them thru (you know who I'd recommend
) make sure the delivery requires a signature!
Get email communications from shipping company for every step of the process.