You're in Tennessee--aren't there 4-wheel drive specialty shops around? Old Jeep folks should be able to take care of you with no problem. I'd call them up, and explain the symptoms focusing on the Dana 30 aspect, keeping the fact that it's located under the butt end of a Volvo secondary.

Working on the guts of a differential is not something you should trust to just any mechanic. You need someone with experience. If they say no, installing a used rear axle is more likely to end in success than having someone who doesn't know what they're doing try to "fix" whatever's ailing your diff.

John