Driveline Replacement, '85 4x4

I'm about to get my first wagovan, and the only thing it's needing is 'a new driveline within 6 months to a year.' All of the other major components have been gone through... New clutch, carb, brakes, compression tested at 130psi, timing belt, thermostat, alternator... It has 240k on it. Any idea how much it'd cost to get a replacement driveline? And how much of a pain in the ass is it to install?