Sounds like something is seriously wrong, as you already know, could be one of many things, even drivetrain going off your comments. So when you are in reverse on flat does it need accel to move ? or in N can you push it ?
Like all imports, get ALL fluids changed (oil,tranny, transfer, R diff, F diff, brake, powersteer, radiator), plugs/filters changed, as most of them would be original Nissan.
Does it idle smoothly ?