As far as I'm aware their is an electronic clutch unit in the rear diff. Your car obviously won't have that or probably the electrics to drive it. The connection on the gearbox is different, you will need a transfer box, propshaft and diff, rear drive shafts and hubs.
I would guess its more trouble than its worth and that is if it is even achievable. Unless you actually need 4wd I would stick with 2wd, 2wd reputation is better than 4wd. Richy