I would say open the claim. They might try and say that it's not in the "same condition" so you might as well open up a dispute in PayPal. Keep working with the seller but having the dispute open helps.
Send it back, but SAVE your tracking #, PayPal will ask for this.
If the seller doesn't give you a refund, you can escalate the dispute and PayPal will most likely pull money out of the seller's account to refund you.