Remove door mirror without taking door trim off?

[HPsauce]

This is an interesting conundrum and I think there "ought" to be an answer.

I have a replacement nearside folding door mirror mechanism (acquired in exchange for a number of Her Majesty's flexible beer tokens from our hosts) as mine is a bit "random" on folding.

The instructions start with the rather tedious process of removing the door card, which quite frankly I'd rather avoid.
There are actually no details of removing the mirror itself and I can find no photos of that area online, but I "presume" (dangerous I know) that it involves taking off the triangular plastic cover on the inside of the door (above the main trim) and undoing the retaining bolt/screw that holds the mirror to the frame.
It then appears to lift off the captive electrical connector and of course the secondary electrical cable needs disconnecting, with the complication of the connectors being deep inside the door - but I can probably deal with that .

I can't see how the triangular cover comes off, is it possible to do that without removing the main door trim, or perhaps just "adjusting" it slightly at the edge? Is it for example just a push (clip) fit or are there some screws too?

If I can remove that and then get the mirror off its mounting, I'm fairly comfortable with (carefully and individually) cutting and splicing the wires in the cables (7 in mine I think) and getting the new unit in.

I'm hoping someone who has "been there before me" can offer some advice. Fingers crossed.