I'm very sorry to hear about your dad.
Someone above mentioned the AudioKarma site, and I'd second that. It's an excellent place to learn about vintage (as in, "I'm not old. I'm vintage") gear or to just discuss it with others.
Nakamichi... great gear, especially their cassette decks. The Nakamichi Dragon makes an appearance in Nine and a Half Weeks in Mickey Rourke's apartment.
But, like everyone else on this board, the folks on that other site will ask for pictures (or at least complete model numbers) so that they can give you better advice on what to do or what to expect to get for it.
There are auction sites that specialize in high-end audio gear, too. There's even a "For Sale" thread on Audioholics.
Once again, I'm sorry for your loss, but, and it sounds like he did, if your dad kept his gear in good shape, you should be able to find a happy home for it with someone who'll treasure it as much as your dad did.