Injector pump issues may be simply need of new nozzles, or even a purge.
May be new motor mounts are in order.

Oil cooler lines can be problematic, when removing them from the radiator, some folks have a hard time there.

Driveshaft, inspect the center bearing I haven't heard of them going out of balance.
The u joints are "staked" in, meaning once installed, using a wedge device or screw driver, hammer on the surrounding metal to push/mangle some metal to keep 'em in place. Are the u joints bad? an inspection should reveal yes or no.

Differential, inspect the rear sway bar links. R&R the diff fluid. Make sure to remove the fill plug first!

Tie rod and drag link, are the ball joint boots torn? If so, not a bad idea to replace them.

There is an intermediate lever repair kit that may be a bit tricky, but depending on your skill set, a DIY.

Depending on the severity of the driveshaft issue/s also a DIY as most other items.

Your mechanic may mean well, but get a second opinion. Ah, that's what doing here...

__________________
83 SD

84 CD