i think you should go for it. especially with a complete parts car. a driveshaft is easy. cut off one yoke from each driveshaft, and have a shop make a new one (you may be able to use one existing drivehaft, depending on length.) around $150 in this area.
fuel tank is easy when the parts car is right there. all kinds of room in a pickup.
i wonder what bolt pattern the rims are? you could swap in the benz' rear axle and keep benz-size tires, maybe even the benz speedometer.....
if bolt patterns are different, you could always carry one benz spare, and a "space-saver" chevy spare.
the transmission tunnel/firewall can be modified with a sawzall
wiring shouldn't be too bad, all a diesel needs is fuel and air.
i think engine (and transmission) mounts will be the hardest, depending on your mechanical ability. which appears to be pretty good
so overall i think its do-able.
oh yeah, try to find a buyer for your chevy engine and transmission before you pull it. its easier to sell a motor when the buyer can hear it run.