The seller is misrepresenting the car if he says anything about "NISMO" in the description, as it's simply an Infiniti G35 with manual trans (they all came with the Sport package, including Brembo brakes).
The price seems a tad high, but the miles are relatively low. I'd wonder why it needed a clutch at 63k (maybe it was driven too hard)... I'd also want a lot of pics of the undercarriage to look for rust.
I owned the same car (mine was DIamond Graphite) for 4 years and loved it. It's a well-built, reliable, modern classic and still looks WAY better than any STi.
Welcome aboard.