Elcapitano

Hi all, my father was a fantastic guitarist. Unfortunately he has Alzheimer's and can no longer play. My mum has asked me to look into value of his Gibson CS 336. She's not sure whether to sell it or not. I said I would find out. I think it was created in 2002. It is black. Can any of you guys give me a steer on this as my mum is pretty emotional and I don't want her getting ripped off. Thanks in advance Elcap