Once a seller drops an item off at the post office, it is out of their control.
If you think someone from customs stole it I would open a dispute with paypal, although I'm unsure how you would prove it was stolen.
The ride quality will horrendous with springs. You would be better off with just getting coil overs from the start.
If you go with springs, aesthetic-wise your look will look lower but you're putting extra weight that wasn't intended on your factory struts.