Is there any reason to be skeptical about the A/C? I don't mind getting the 60k service myself, but will use it as leverage to lower the price. Should I be any more concerned about the clutch.
You should be concerned about all of these issues. They might be fine, they might not. I recommend arranging with the seller to get the car inspected at Acura of Brookfield, in west suburban Milwaukee, which is the nearest dealership to Racine and which has a lot of NSX expertise. That way you will know what work really needs to be done. (You might also try calling Acura of Brookfield to see if they have any service records on this particular car.)
As for those particular items, since the A/C isn't blowing cold air, this could be anything from a minor leak in the system, to a failure of the climate control unit (username Briank
repairs these and is located close to Acura of Brookfield), to a compressor needing replacement for a lot of money. Just recharging the system will almost certainly not cure it. And the fact that it has not been fixed is a red flag; what else on the car isn't working and needs fixing?
It sounds like you may be confusing the 60K service with the timing belt and water pump replacement. There is a service recommended for every 30K miles or 2 years, consisting of replacing the fluids (oil, brake, transmission) and filters (oil, air, fuel) and a valve adjustment, and it generally runs around $900-1200. Note that this should be done every two years if it doesn't accumulate the indicated mileage. There is also another service recommended for every 90K miles or 6 years, to replace the timing belt; the water pump is normally replaced at the same time, and this runs $1500-1700 (in addition to the 30K/60K/etc service). It's a good idea to replace those 14-year-old cooling system hoses at the same time.
The owner says he has all the service records, so he should easily be able to tell you how many miles and how much time since the last time it had all the fluids and filters changed, since the timing belt was changed, etc.
As for the clutch, clutch lifespan on the NSX varies. If the clutch slips, it needs replacing; otherwise, it doesn't. And unless it's starting to slip, I don't think you can tell how worn it is unless you take the transmission apart, which involves a lot of labor (just like the clutch replacement).
Note, I'm NOT saying there are problems with this car. If it all checks out, it could be a great deal. However, these are the steps you can go through to answer your questions and reduce your risk by identifying how much work you will need to do to this car. If you don't, then you may have to repair each of the items noted.