Here’s my more detailed write-up on the process of removing the old LCD from my Analog Keys and replacing with the new OLED display module from @zigmars . I want to thank him for the work it took in designing these modules and producing them. I do highly recommend the module, it looks excellent and improves my experience of using my AK 
As for the replacement of the display board itself (desoldering / soldering) it should be about the same process for other devices (A4 mk1, AR mk1). But for the disassembly of those units, you will need to look elsewhere for instructions.
I’ll start by saying I’m not particularly experienced with soldering, and in general this project was pretty involved, including the use of several tools and a good bit of time. I’d guess that from disassembly until it was all back together, I spent 3 or 4 hours on it in total. I am a slow and methodical kind of guy, certain tasks I took extra time for, out of fear of messing up an expensive keyboard. Perhaps a confident solderer could get it done in 90 minutes - I’m not sure.
If you’re completely new to soldering, I do NOT recommend you try this without getting some experience with soldering components first.
Disassembly:
Remove the knob caps from the front panel. Master Volume, Level, the ten A-J data encoders, and the big Sound Selection knob (13 knobs in total). You should be able to pull them off with a bit of force.
Find a stable work surface on which to place the AK, and lay down some soft material to cushion the face of the keyboard from scratches. Be mindful of the joystick as well when laying the keyboard upside down. You should lay it so the keys are facing you.
On the bottom of the AK, there are 28 size T10 Torx / star fasteners. The ones I’ve marked with red dots hold the back of the case on, and the ones marked in blue secure the keyboard to the case.
For disassembly I don’t think the order in which you remove them particularly matters, but I marked them because for reassembly I believe it’s easiest to fasten the keyboard screws first.
When all of the screws are removed, you can lift the back of the unit slowly and very carefully. There is a circuit board that will still be attached to this panel. Lift from the front and slide the panel to the left slightly before lifting up, so the circuit board can clear some metal tabs on the right edge of the case. Tilt it up and away from you slowly, keeping in mind there are three cables which need to be disconnected before you can remove the panel completely. The wires do not have a lot of slack, so take care not to put too much tension on them. Disconnect the following:
A power connector (on the left in the photo, two white wires):
And two 10 pin connectors:
I made a mental note of which way these connectors were facing before removing them, so I wouldn’t accidentally turn them 180° later when reconnecting.
After disconnecting those from the board, put the panel with attached PCB somewhere safe.
There are now two cables connecting the keybed to the front panel circuit board which need to be disconnected from the circuit board - a blue 4 pin connector and a red 20 pin connector:
(My 4 pin connector was pretty loose to begin with, which is why it is not sitting straight in its socket)
Once these are disconnected, you can remove the keybed.
In the last photo, note the 40 pin connector in the bottom left. It goes from the circuit board to the LED array for the keys. This needs to be disconnected next:
This one was a little stubborn, as there is almost no slack in the ribbon and the connector was very snug. I think it’s easiest to remove it while the circuit board is still fastened to the case (unlike in my photo 
).
Now there are a great many T9 Torx/star fasteners holding the two remaining circuit boards to the front panel (I forgot to count how many screws). Remove them from both of the boards. The small joystick board is directly connected to the large front panel board with a 20 pin connector, and I found it to be best to leave the two connected until you remove them from the case. The joystick board cannot be removed by lifting straight up, as it won’t fit past the screw tabs. So my approach was to lift the left side of the larger board carefully while supporting the small board (to avoid bending or putting too much pressure on the connection between the two).
Once the small board is tilted up as shown, it will clear the tabs and you can lift both boards out together. Then you can carefully pull the boards connectors apart and put the joystick board somewhere safe.
Now you can turn the front panel PCB over and reveal the LCD.
(cont’d in following posts)