Kurt,
I am hoping you are still following this - so here is an update on the Evolve 75 - which is what you have on the photo.
Do NOT follow the evolve 65 instructions - I did and broke one of the tabs.
Instead on the OPPOSITE side from the one you are showing on the photo you will notice a small Torx t5 screw.
Unscrew that one, and one that side will popup. The opposite side comes off by lifting up the orange speaker holder slowly to around 30 degrees and it simply unhooks. the speaker wires are very tiny so don’t pull too hard.
the rest of the stuff is held in place with Torx t6 self tapping screws into plastic, INCLUDING the back cover. once you take those off you have access to all boards and wires. -
so that is how to open them up.
Downside - my microphone still does not work, so I suspect I may have broken links from the microswitch to the board - it has a tiny printed links on a tiny capton tape so I may simply solder the microphone directly and mute and unmute with the buttons instead of the boom
Hope this helps - bot sure when I can get some photos - But with the approach above it took me all of 5 minutes to open the boom side of the headset. the other side should be just as easy -and that side is the one with the battery. there is a youtube video on how to replace the battery on Evolve 75 -which is where i got the information on the torx t5 - credits where credit is due.