You can cancel. You will be allowed to re-use the funds but there will be a $50 change fee for resusing them. (In other words you would only have $42 to spend on a new airfare)
Same thing on change, it's $50 plus any fare change amount.
Thank you for your reply! I guess any credit would be better then none. I really wanted to book with Southwest since they give you credit for your travel, but the fare from PDX to MCO is aweful