I can tell you that even if you remove the window winder mechanism, that you need the hands of a small lady or child to get them up inside the door!
As luck would have it, I am a small framed man myself, and could mostly get my hand inside the door with the window mechanism out, but I still struggled and resorted to nuts taped into the end of ratcheting spanners and of drilling an access hole under the area that would be covered by the door card in order to fit new mirrors to my car.
Make sure that any after market mirrors you might wish to fit have enough rise in them. Mine sit too low in the door to really be of use.
I would recommend the clamp on type that just grip the frame, much less hassle! Haha.