there are definately more than six 1998 series 3 vspec gtr's in australia.
If he is telling you all this stuff that you have mentioned, it seems that he really wants to get rid of it and you have to question what else he is hiding and what else he is prepared to tell you to make you buy it.
the very late 98 vspecs had leather seats and those are the collectors items that are worth money - apart from this there is no difference, just some sellers believe the 98 is worth more, but this is not the case.