Get hold of the gearshift ECU from an R34 25GT, it's seperate from the main ECU unlike the turbo models and will be easier to fit, it will control the tiptronic just fine.
Also you'd be better off not fitting the NEO it has a 1000 and 1 sensor inputs unlike previous models which make it a pain to fit, just go for a standard RB25DET.
If it's any help, putting a NEO RB25DET into an R34 25GT is enough of a pain, it looks for traction control inputs, ABS, boost sensor inputs, different speedo signal etc etc etc