I have a 13 inch MBA with 4GB memory, 128GB SSD, it was purchased as a refurb from the Apple store and is less than 6 months old. I'm thinking of selling it on Craig's list and using the funds to upgrade when the refreshes come down. The MBA has had a Wrapsol skin on it since day one, it also has Apple care through Dec 2014. What should I ask for the system? Thanks in advance for your help.