300SD transmissions

[VA300SD]

Hello, owners of jerky transmissions.

Previous owner of my 81 300SD replaced the tranny with a rebuilt (or maybe used) unit at a "garage", not an independent MB shop. (One example of their work is epoxying a tear in the fuel tank instead of replacing it - the patch job developed a slow leak and diesel mess in the trunk. I replaced the tank and decontaminated the trunk.)
The transmission had a severe clunking (or jerky shift) from 1 to 2, bad enough to be concerned for the differential which was taking a pounding if the throttle wasn't modulated during shifting.
Also, there is a flare from 2 to 3, with the RPMs rising about 500-1000 rpms during the shift.
The local MB dealer shop took care of the horrible 1 to 2 shift, but not completely.
The MB dealer shop printout says....
"Checked and adjusted the transmission pressure", and charged $48 for one hour labor.
No parts involved.
I still have to let up on the throttle to avoid the jerkiness.
And finally to the question -
Is it possible the "garage" just swapped the tranny and did not complete the job ? What kind of stuff can I look for that they may not have completed such as final adjustments and settings ?
I suspect "bubba" workmanship and would like to eliminate some suspicions before moving on to other possible causes of this shifting problem, especially before it ruins the differential.
Also would like to be aware of potential catastrophic failures due to inexperienced and negligent shops tacking MB transmission replacements.

Besides this very annoying problem, all I have to do is change the coolant, replace three rubber air filter housing cushions, and keep an eye on the exhaust hanger donuts and this car is ready for another 100,000 miles. (Actually, I am also pricing a rebuilt cruise control amp and diagnostic plug from the Parts Shop.)

Thanks.
Alan
81 300SD 190,000 miles.