I bought the trim ring/housing (#5 above). I haven't installed yet but pretty sure you need to take off the door panel to be able to release the housing. The motor and glass are separate and can be swapped over.
08 E90 | Jet Black / Black | 6MT
Mods: RAC RG63 w/ Pirelli Corsa 255F/285R | Akrapovic Evo Exhaust | OEM Blacklines
Winter Setup: OEM 18s w/ Nokian Hakkapeliita R 245/40-18