but I have a situation, I don't know the correct amount that I should put in the check to renew, how do I do?
You can send a check payable to the 'Commissioner of Motor Vehicles', but do not write the amount
How do I request a refund? even so I changed my name
yes, you can. First, you have to surrender the vehicle plates at a DMV office and then request a transfer receipt, not a refund receipt. Secondly, you have to send some items to the address on the Request for Refund MV-215 form.