Dave,
What engine are you fitting?
Is it a Crown, Soarer or LS400.
They are all pretty easy to wire up if you put a little research into it.
Having it done could cost as much as the motor and having an aftermarket system installed and tuned up to 4 times the cost of the motor.
To do it yourself will cost perhaps $100.00
If your wiring and soldering skills need help surely you have a mate who can assist.