I am booked in June EWR-LAS in W class. I have no elite status but miles to spare. It's giving me the option to use $100 and 15,000 each way to be put on the waitlist for upgrade. If/when the upgrade goes through would it be well in advance? day of departure? if it doesn't go through does the money and miles automatically get refunded or will I have to call to request it? Any advice or insight is greatly appreciated.

Thanks