My insurance simpy states that unless I have an alarm/immobilizer with all black wiring installed my theft excess is higher. (Shannons)
If the plan is to keep the car on the stockish side with mods more on the asthetics side (aka rims, stereo etc) then service costs and fuel costs won't be that prohibative. But the hard part with skylines is not giving in to the modifying bug.
If you start modifying, you'll have to service them more regularly, you guzzle a lot more fuel and you'll run the risk of more things breaking. Otherwise I don't see too many issues for you. And at 36 I see far less Police issues than your average 21yo will get. I'm 30 and have never been pulled over (touch wood) - except a couple of time by guys just wanting to have a look at my car just to check it out (which should be illegal!!!!)