The easy fix, if you can find one at a reasonable price, is to get a used differential and swap them. No setup, just remove the axles and swap. Take care, the diff is HEAVY! This is what my mechanic does, he isn't very good a trannys or diffs.
Otherwise, I'd find an indy mechanic familiar with this type of pinion adjustment (I think it is fairly common, reguardless of make) and talk to them. Other than getting the location correct this isn't a really big deal and can be done in the car.
Someone with experience can help you get the depth (ie turning torque) correct without risking excess backlash, etc. I'd not experiment without knowledgable assistance -- it's too easy to snap a tooth off the ring gear! Do not, under any cirucumstances, more the rear wheels with the pinion loose -- the weight of the car moving can break teeth off the ring or pinion gear.
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!