Thanks Guys for your opinions,
I'll check out the bonnet and such if it's legal, as I'm going to be on my P's I won't be able to drive a gtt hence why I'm looking at an N/A version. My thoughts are that I can either convert this car to a turbo or just sell it and buy a GTT when I'm older. Hopefully the prices will go up for N/A Skylines as by the time I sell it they'll be legal in the USA, hence I can sell it for more or around the same.
I'll try offering him 17k or around that. Still interested to hear what other people have to say and what they think about my theory with selling it later on.