You can call customer service to found out. It might be listed on your bill. You can also look up the remaining balance on your my Verizon account online.
I'm most definitely NOT a VZW employee. If a post answered your question, please mark it as the answer.
How much would I owe to pay off my device?
This would depend on which device you purchased, how much(if any) you placed as a down payment and how many payments you have already made on your payment plan. But as Ann154 said, the amount due should be available on your bill or your MyVerizon account.