I think there are at least a few listing permutations:
- calibrate to prove it's 100% good to go
- get a DMM and show proof all the functions at least work
- list as unknown, don't even turn it on
In all cases I'd probably suggest listing it as-is, no returns, just to avoid drama.
Could try listing it here on the EEVblog marketplace forum, although it seems more like something a company would want vs. a hobbyist.
Seems like no matter what you should expect $2k - $3k for it.