Bloody good choice mate
First up, I'd rekon you should take a good look at the VP series, too. VN and VP are basically the same, although some bugs were ironed out on the series 2 VN, and the VPs. They also have a slightly more sensible radiator setup; and in terms of parts for repairs, they're all interchangable anyway. Take a look at the subtle differences in body style to decide which one you want too. (headlights, boot garnish, badges, window gutters, etc.)
When you inspect the car, have a close look at the little things. See if the roof lining is firm or coming loose, check ALL the door seals and rubbers (give them a good tug to see if they come loose), get a mate check that all the tail-lights illuminate properly, check for water leaks in the boot, and pop under the car and take a look at the sump, to see if it's badly warped. (common problem, but not always critical). something with less than 200,000ks on it is a good buy, but check for service records etc to see if this is the actual distance the car has travelled.
If you're after a car that's been treated well, take a quick look at the back-right tyre, and compare it to the back-left, just to get a quick idea if the last owner's been ripping skids, too ^^ This could mean problems with your tailshaft bearings, diff, and other things down the line.
Also, make sure you test-drive three or four different VN/VPs if you get the chance. They all drive a little differently - you may even find a freak that makes a little bit more power than the others. They're like that.
For a nice specimen, look to pay between 1000-3000 dollars, like xcop said. Be very weary about something cheaper, or unregistered, as it could end up costing you big bucks down the line to get it into roadworthy condition.
Out of interest:
I bought my 1992 VP Executive with 192,000 on the clock, for $2000, unregistered, without rwc. It cost me $1000 to get into roadworthy condition, and $700 for stamp-duty, registration, and plates. All up: $3,700 on the road. I would have gone for something cheaper, but this car came with full service records, was formerly owned by a middle-aged man as a fleet car, and had a reconditioned auto, new alternator, new tyres, new battery, and drove VERY smoothly compared to others I'd driven.
Here's some pics of the condition of the car for that price, as a comparison:
http://premium1.uploadit.org/Fargoth//daniels_car.jpg
http://premium1.uploadit.org/Fargoth//daniels_car2.jpg
