I'm doing the 82 300TD. The setup is basically the same. Maybe a few minor differences. Look at this post for the front

http://www.peachparts.com/shopforum/diesel-discussion/60560-300td-suspension-rebuild-progress.html?highlight=front+end+rebuild

look at this one for the rear.

http://www.peachparts.com/shopforum/diesel-discussion/60964-300td-rear-suspension-rebuild.html?highlight=rear+suspension+rebuild

A shop manual will give you alot of insight on the 126 rebuild.

Dave

You can replace the trailing arm bushing without removing the whole rear assembly. It does require some tools.
Jack stands
Hydraulic floor jack
and of course the normal tools for removing nuts and bolts.
17mm
22mm
and 24mm
crow bars
silicone spray
and my favorite

http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=38335

used this on both the front and rear rebuild

you can unbolt the subframe bushings and the subframe will still be suported by the differential mount.
I found it best to remove the trailing arm completely to r+r the traiiling arm bushings. Just not enough room to work on the bushings with the trainling arm in the car.
To remove the trailing arm you have to remove the coil spring and hydraulic strut. Disconnect the brake hose, sway bar link and its easier if you remove the caliper and rotor.
Once you have r+r the sub and trailing arm bushing you can now r+r the differential mount. Then the rubber is all new for you.

As I said review the Shop manual and my posts. Also look ar Thomaspins web site.

http://www.peachparts.com/shopforum/tech-help/61622-w126-differential-reseal-refill-illustrated.html?highlight=thomaspin

Dave