I would suggest taking it to a reputable dealer like ninhonto.ca and seeing if they are interested in consigning it. That way it is in their best interest to get you the best price and they have the expertise to know what it is.
Their site is worth it just for the incredible ninhonto screensaver. I would be surprised if it was worth less than 10 grand.

Right now could be the best time to sell a ninhonto as they are incredibly overpriced at he moment. Movies like Kill Bill and the japanese government banning exports have driven prices really high. It seems like every cheesy stock broker or TV exec in the US wants one mounted over his desk as well.

I would sell the ninhonto and buy a few euro napoleonic era and smallswords as well as some good examples of early sword bayonets especially the pioneer models. With the cash left over you could probably buy a nice motorbike as well.