I was quoted similar pricing when I rang around for mine, Thats exactly what I had to do on my VK the engineer cost $250, DB at an exhaust shop was $25 as the engineers unit was away getting calibrated, weighbridge ticket was $20 (it will come in at 1500kg I dont even think they weighed mine). The better the car is presented the better pricing an engineer is going to charge you, if everything is neat, tidy done properly you wont have an issue.
My only problem was a noise test first time through it came in at just under 96db it had to be no more than 91.4 so I went away refind my exhaust came back and tested at exactly 91.4.
The other thing you havent covered I had to run an unleaded filler neck which wasnt an issue for me as I am running a 90l VQ EFI tank.
Not only do you need a front brake upgrade you need discs on the rear.VB-VS rear discs will suffice. I run VZ ventilated rear discs on my VK and VZ twinspots and 300mm fronts
My car was engineered by Lakeside Engineering Kevin has now retired he is very well respected in automotive circles, the only grumble he had with my car was the passengers side headers only having 6mm on clearance on the chassis rail he would have liked 10mm but it wasnt possible to fit the headers in the confined space so after some tests reving the engine and seeing clearances it was passed. I have never had a provlem with the pacemaker headers hitting the chassis rail anyway.
cheers
Scott
best of luck