Absolutely brilliant! Thank you for all of that detail, Kaz! Great idea on applying mild heat; this should be attempted above 20C/70F.
I can add a view of the unit, at least. The connector receiver plastic will slide out with the PCB from the main housing. Here is a "bottom" view of the unit; one must apply force to pry the tabs open (shown within the yellow rectangles), but patience will win the day. If I recall correctly, only one needs to be freed and the other will have just enough freedom to pivot/slide out with less effort (focus on the side that is easier to reach). If you have a plastic trim removal tool, or a small pick, you can use it as an aid to hold "separation progress" on the long edges as you work with the screwdriver on the main tab(s). Patience will win over brute force!
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The PCB edges are contained by "C" channels in the main housing, and it will just slide out (no additional prying necessary once the bottom cover is free, just a straight pull toward the floor). With the connector/harness out of the way, there might be enough room to slide it out without removing the housing from its mounting bracket.
Then, the target is in full view:
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Just make sure to slide the modified PCB back into the housing in the correct orientation to fit into the "C" channels.
