Driver's side mirror replacement

[Tesla1]

Hello to all. I have a 2001 X5 that leaked the oil out of the driver's side mirror and is now concave. I talked to the dealer and was told that I had to replace the whole housing. I found a replacement mirror housing on ebay for half the price but the cost to switch out at the dealer is outrageous. I saw one thread that stated that the housing is able to be disassembled but am I able to replace the mirror itself or do I need to replace the whole housing? If so, how do I go about getting the door panel off? I searched and tried to look at the folding mirror retrofit but the link directs me to a blank page. Thank you for any ideas.