USB Midi Controller Modification?

Okay, I have an old Korg Nano Keyboard Mini Controller. I'm wondering if it's possible to use this as a base to build a more functional midi controller, i.e. replace a few keys with rotary knobs to make it more compatible with what I want to control in my CrossDJ software. If so, could someone direct me to a site or book/information on how to do it? I haven't torn it yet, so I'm not sure what kind of wiring goes to each key or what kind of wiring is needed to hook up to a rotary control. Thanks in advance for any help.