Hey mate, I test drove all the R34 GTRs on sale for a decent price in Melbourne a year and a half ago, including that one, before I ended up buying a different R34 GTR. Can't believe it's still on the market.
My, how the price has dropped. He was asking 60k or so at that time. He's a real nice, decent guy, and will let you take it on the freeway to test. He even showed me where there had been some (minor) panel damage before and re-sprayed. As I recall the front lip has a crack in it somewhere, but otherwise it's quite immaculate. Honestly, I wouldn't have noticed if he didn't tell me. He modified it and services it at Racepace, if I remember it correctly.
I would've bought it from him if it had been a few grand cheaper, as the yellow colour is really unique, but I ended up getting a different one. Take it to Racepace for a mechanical inspection/compression test or ring Ben there to see if there are any mechanical issues, but I doubt you will regret buying it. He seems like the kind of guy who takes care of his cars. Keep in mind though that I saw it 18 months ago, so a lot could've changed since then, although unlikely if it's the same owner.
Good luck and let us know which one you end up with.