I recently purchased a complete but IVA failed zero. I needed access to the dashboard area to address one minor wiring fault and had to take the whole scuttle apart!
As others have said, if you have an all in one dash I would recommend making the dash removable. It's not expensive to do but is time consuming, hopefully the finished product will be worth the effort.
I have taken a few photo's as I've gone along which should give you the info needed, but can't upload them at the moment as we have the builders in doing some construction work on the house.