In my experience, early dashboards are not attached to the black crashpad, but later models 1974ish seem to have the crashpad glued and stapled to the back of the wooden dash.
Removing the early dashboards is just a matter of unbolting it, but getting the new dashboard in is very difficult because of the wiring, and because the ends around the eyeball vents are a very tight fit with the crashpad. I managed to damage 1 dashboard on the end levering it into place.
To get the crashpad out with the windscreen in place is a "challenge" as it is held by 4 long self tapping screws through the two demister vents, which are very close to the glass. Special ratchet screwdrivers would be needed.