sounds like you need to find a mechanic that knows what he is doing
he is quoting you a stuffed engine as either he wants nothing to do with it
or his kids need new braces on their teeth
as your in WA, give Matt at United Fuel Injection a call, and see if he can help you
he has forgotten more about the nissan motors than most will ever know - (not affiliated, just had awesome service everytime I have been)
finding good mechanic's in WA who know the Patrols is difficult, but not hard