Just replaced it on my 1273A, the old one came off easily with hot air and gently lifting it off the PCB pads. A little heat on the display itself and it came off the backing easily enough. Kept the old foam backing, with a few dots of CA glue (probably good enough). Might have worked to use double-sided 3M tape as well... The hard part was soldering the new connector to the PCB; I cleaned up the pads and applied solder paste, but couldn't really reflow the connector as it was a $*$&^* to get to lie flat. I held it sorta in place with a small clamp, then pushed down on it with a small screw driver and gave it a quick tap with the solder iron (JBC CD-1SQF with a fine tip) and the paste flowed perfectly. One pad/tongue at a time: push it down, tap with the tip, remove tip, hold for a second or two, move on to the next. I did it under the AmScope. Reassembled, works fine, except it's right to left, shifted (as expected). Time for the firmware fix; haven't actually looked at that yet, but I assume the unused white connector to the top right of the main PCB (rear view) has rx/tx pins.
Clearly these displays are defective... Amber OLEDs have very long life, blues are shorter but not THIS short by any imagination. I use mine very little, and the display didn't even outlive the batteries that came with it. (Which were probably due to be discarded anyway, not a fan of leakage.) From what I can tell the most common OLED defect is they're not properly sealed, air gets in and oxidizes the <whatever is inside>.
Edit: here's the exact item I got:
https://www.aliexpress.us/item/2251832698680234.html(Apologies for resurrecting this old thread.)