What is the procedure and do's and dont's in replacing the driver side mirror along with the body shell covering the mirror?

This applies to most mirriors since year, make and model are not given. There should be a cover plate on the inside that pops off. Some do have a screw holding them. Remove this panel and there should be either 3 screws or 3 nuts holding the mirrior on. If it is a power mirror you will need to unplug the wire which you should be able to pull up enough widthout removing the door panel. Simply remove screws or nuts and the mirror will come off. Reverse the process with the new one.