agree a normal mechanic is a good start
most mechanics can sort out most normal EFI problems etc
its only if you need specific help with the 4wd system in a GTR, or want a 600HP build, or some pecular item relating to a skyline
its a car with a std EFI system and basic sensors, most mechanics can sort it out
even a plus if you can get your own consult, is take the car to them with consult, and its christmas
they can do all the normal work, and get access to the onboard EFI and fix away