As long as you follow the Money Back Guarantee 'rules', you will get a full refund.
Give the correct reason when you open the case.
Ask Ebay to step in after 3 days if you don't get a label from the seller.
Return the item promptly and upload the tracking if you need to. Sometimes it is uploaded automatically.
The seller has 48 hours after tracking shows they have the item back to refund you in full.
"There are two ways to be fooled. One is to believe what isn't true; the other is to refuse to believe what is true.”
Søren Kierkegaard, Danish philosopher (1813 - 1855)