The ARB Bar I have fitted comes with comprehensive installation instructions which give all the measurements an installer needs with pictures, but no template to mark with.
Im hearin ya - I wouldn't of even been able to watch them do it to mine
Involves a lot of cutting and you would need the right tools and experience to do a good job i think. Final finish is important when you spend that much money.
I guess it depends on how reputable your 4x4 dealer is......