Help, my cell phone died.

It's an older model Verizon LG VX4400 but it's a phone I love and want to replace.

I see Verizon LG VX4400 phones listed on eBay from reputable sellers.

I hope to buy a phone on eBay, then take it to a Verizon store and have them delete my dead phone and add my "new" used phone to my account.

What questions should I ask sellers before buying a used cell phone? How do I know used cell phones are free and clear for me to add to my Verizon account?

Thanks for any help you can give me.

Kessa