I have seen how an old M3 can cost 10k for a major service inc GearBox and was wondering how R32 GTR's compare to a normal car when it comes to maintenance/servicing.
An R32 GTR will cost more than a 'normal' car to service as you have to do oil every 5,000km and some parts if you buy new can be a bit expensive. But nothing like $10k for a major service. Euro cars are the ones to worry about for that.
Should I look to spend 30+ and get one thats had upgraded turbo/s and N1 bits etc or go for a Clean Low KM stocko for under 20k.
I think a mid point would be better, but bare in mind that there are some really bad examples around that are ticking time bombs and an engine rebuild is NOT cheap.
To turn a stocker into a reliable weapon but not crazy are you talking big $$?
Not an easy one to answer as 'weapon' can mean different things to different people. If you were to get a rebuild, forged internals, gt-ss turbo's, ecu, fuel pump, injectors, etc I would say about $15k would make a pretty reliable and very powerful gtr (around the 320awkw mark).
How many KM's is high for a GTR?
Most have been wound back, so the number in the dial is not a good guide. Asses the car based on wear and tear inside i.e, steering wheel and gear knob, seats etc (if these parts are stock...) and more importantly if you find one you think looks good, get a mechanic to inspect it including a compression test before you buy it!
Drivability? Around town etc
Well generally they will have lowered suspension, exhaust etc so they are not really a car for around town in my opinion. They have a pretty shocking turning circle and if you are anything like me, there are plenty of places you won't park it. While mine is a 'daily' I don't always have to drive for work and for times I don't want to use it I have small economical cars i can borrow
Hope that helps answering those questions. My only other advise is that you may have to be patient to find the right one as there are quite a few out there and the prices range from dirt cheap to quite expensive. In general you get what you pay for... but either way make sure you get it checked! Otherwise you may find out the hard way that a cheap GTR is anything but.