I don't have permission yet to post these on here so I'm posting a link to photobucket. I hope it works and please forgive me for the poor picture taking. I am not a professional and these are just taken at my house of the lens.
KEH will buy it or lots of other photo dealers. They would buy to re-sell so you won't get top dollar that way.
But, you avoid the hassles and the scammers that will likely arise when trying to sell to an end user yourself.
I tried to buy one of these at a local estate auction about a year ago. The auction was also an eBay Live event unfortunately for me. I was the high bidder in person, but someone online snatched it away when it went over my budget.
At the auction there was lots of great Nikon gear. If I remember correctly, the 300mm f2 sold for about $6000. The TC14c was separately sold for about $500. I did not see the trunk case included.
There is currently a modified 300mm f2 on eBay right now asking about $8900. It has had offers below that number for the past month. It is modified for motion picture use, but can be used on still camera with the right mount. I hear the modified version usually goes for more since there is more demand and deeper pockets for this lens on motion picture cameras. For collectors, the original is more desirable obviously.
I would still consider getting one of these in useable condition. I wouldn't call myself a collector, but would pay a premium since I take a lot of available light indoor photos.
Go to the Nikon Forum and then post it for sale on their site. The Pro's hang out there and they have the bucks to buy it. According to the moderator its worth over $20k and is the sharpest lens they ever made. I did not mention the TC, so that adds to its value as well.