I have a big problem with FedEx France, they lost 3 shipments of PSU's, and they admitted that the shipments had been lost
They asked me to contact FedEx China

how stupid ??
What should I do? Can I sue them?
I would come to an online forum with many international posters and ask for legal advice over ~$600 in PSUs also. Sounds like a good plan. Litigation and the expenses really would outweigh any chance of benefit.
Honestly, I would sell the D3s you don't have PSUs for and cut your losses now. The D3 is not going to get more valuable. It is much more likely to only get less valuable as time passes.
Good luck with FedEx.