If you have this done professionally, your looking at serious money.
There is easily, and i'm not kidding, +-100 hours of work in this (an absolute minimum of 60), some of the stuff is piss easy the steering wheel, cluster, nav unit (or even standard radio) is going to take you hours and hours.
Also, there is significant amount of risk in this, cause if you break something, you have to replace it, and with old fragile plastic, breaking it is very possible, not to mention super fine electronics that you have to do almost surface mount soldering on.
That's why you see so few of these going around, Its too much work, a great deal of risk.
If you really want this done, I can hook you up but its going to be psychotically expensive (15kish or more), and to me its just simply not worth it, not to mention the 3 to 4 weeks you will be without your car.