You should not be trusting that shop..
Everyone who knows anything about AC systems knows that if you open the system at all you must replace the receiver dryer... there is no question about that... go to another shop for the rest of your AC work.

Read Hit man X's post and follow it closely... those are all industry standard safe answers...
except that assumption about the hoses... that will be determined by your pressure test with nitrogen and R22 before you do your vacuum immediately before filling your system ...
The part about flushing with regards to the amount of oil in the system is very important.. that is the only way you can know that you have the proper amount ..and that it is clean.... and you can not just add... because too much oil is very bad also...

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1980 240d ,

chain elongation, cam marks reference:
http://www.peachparts.com/shopforum/showthread.php?threadid=10414

http://www.peachparts.com/shopforum/diesel-discussion/305365-9-degrees-chain-stretch.html

evap fin cleaning:

http://www.peachparts.com/shopforum/showthread.php?t=156207&highlight=evaporator

A/C thread

http://www.peachparts.com/shopforum/diesel-discussion/297462-c-recommendations-mb-vehicles.html