I'd get a second opinion. Green oil? It could very well be the evaporator, then again......
Gauges might help. Has the system been pressure tested with A/C gauges? Depending on where the leak is, the gauges might confirm a faulty evaporator.
I studied up on this process last night for a 126 car. It's documented on the CD-Rom for that car. May be for yours as well.
Looks like an absolute mess to deal with. I wonder just how many techs have actally done one or should I say SEVERAL of these.
Hope it turns out otherwise.
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.