Replacing the door mirrors on most cars requires removing the driver or passenger door panel in order to gain access to the electrical connectors that control the electric mirror and heater circuit. To avoid breaking clips and trim panels you need instructions and pictures.
I would suggest you get a subscription to Alldata. It is very reasonably and allows you access to one make of car. All the repair instructions ,service bullitains, component locations ect...
Mostly straight out of the Mercedes manuals. Its the same information we use in independent repair shops.
The repair manuals you get in parts stores are too generic and the Mercedes manuals are prohibitively expensive.