I think if you are replacing a perfectly good working display with a stack one your are clearly just a masochist.
All that expense, and for no gain. They are only really and use if you dont have a dash or loom to begin with.
Anyway, they shouldnt be hard to get hold of, just dont be expecting much change out of a grand.
Ive got a stack revcounter running off a wasted spark ignition, easy to install and I guess a whole dash wouldbt be massively hard. Basically it is just a set of inputs from various sensors. It really depends on what kind of engine management you are running, what loom you have etc.