You have a Word (.doc file) which gives you the Engine Control Module and the AC Wiring Diagrams which also lists what all of the components are.
I have also sent you both of the wiring diagrams as picture files as these are often easier to read from.
If the Air Conditioning is blowing hot all of the time you need to ensure that the system has enough gas. If there is not enough gas then the Refrigerant Pressure Switch won't activate and therefore you won't get any cooling. It could also be the Heater Flap Motor that is stuck in the hot position. You would have to check if the Heater Flap is moving when the Temperature Control is operated.
If the gas level is ok and the Compressor still doesn't work then you need to check the fuse for the Compressor Clutch and it's associated relay. There are also control fuses for the Control side of the system. Check those as well.
If the 'Technicians' you have employed to carry out your diagnosis can't diagnose what is in effect a very basic system then they have no right to call themselves Vehicle Technicians! I would be asking for your money back due to the lack of diagnosis and repair!
If you don't feel capable of completing the work your self I would suggest you take the vehicle to a Mercedes Dealer where they have Mercedes Trained Technicians who also have access to the latest Technical Data.
If you require specific location information for the parts listed in the diagrams then you would need to register for Mercedes B2B which is available here: Mercedes B2B. This is available with various subscriptions available from an hour through to a years access.