Last time I looked, the shop time alone for an A/C evaporator was 21 hours. Multiply that by your dealers hourly rate. New/used/rebuilt A/C compressor I suspect is in the $400-$800 range, plus hoses, new receiver drier and labor. How about the condensor? You may need that too. Then you need to decide if you want to salvage this R-12 system(presumption) or go with R-134a - more $$$$.
Then we get into the infamous valve guide/seal problem the early M103 motors were known for. In a previous post, MB Doc indicated guides/seals were updated in '89...forget the month.
My guess is your wallet will be lightened a bit.
1991 300-SEL - Model 126
M103 - SOHC
James Madison - Oppressors can tyrannize only when they achieve a standing army, an enslaved press, and a disarmed populace.
Liberty Firearms Training - After years of trying to regulate California criminals with a never ending stream of gun control laws they have still not given up with the belief that if they make something a crime that criminals will miraculously start obeying the law.