Can I get my sbg6782-ac surfboard refurbished to sell?

I have a surfboard Sbg6782-ac and would like to get it refurbished  with the latest software so that I can sell it.   I am moving to your Surfboard S33 and there is nothing wrong with my old modem.   I just wanted to upgrade.  I don't want to throw it out but know the software is out of date and dont want to throw it i  the trash.   And NO your ISP does NOT autoupdate….if you own it they won’t touch it contrary to what you say.  Believe me I have argued many times with the Isp.  They will if they own it and give you that modem but if you own it forget it.