Appraising is pointless for selling. You are betting off figuring a good selling price by posting it up on prime and getting opinions from the prime members. Much more accurate and considering that potential NSX buyers are mostly willing to travel the country to get the right car, it's more accurate to get price opinions from members all across the country anyways.
If it's for insurance, again it's kind of pointless. Just get it rated as a collector car and then you can name a fixed agreed value. No ambiguity that way and both you and the insurance company knows the value up front. It's too hard to know how any insurance company will value your NSX otherwise because there are probably not going to be a lot of comparables to base a value on, so it's a crap shoot what value you end you getting in event of a total loss. Better to just get a fixed agreed value up front.
If it's for some other reason other than the above, then let us know what you are looking for...