save your files to a usb and then buy a 2.5 sata drive what ever size and replace the old one that. quick reformat when install and you have a new drive ready to go, and put in the copy files from the usb.
Any sata hard drive will work fine. just pop the side panel off, remove the blue screw then use the tab to slide the entire tray to the right then pull it out. getting the 4 screws holding the hard drive out was a pain but if u have the right size screwdriver it will come out good.
i think there is a bit of thread lock on it. place the new sata hard drive of your choice in and put everything back and then turn the machine on. first thing it will want to do it fomat the new hard drive. then check your system setting to see how much hard drive is registered.