On the 436 the LEDs are on a board and the clock fix also. So they just swap the board. It has an older firmware on it so you must put the new firmware back on it.
On the 536 the LEDs are changed and a battery mod done. No board swap-no firmware change
I just got mine back from the UPS man. I immediately began to panic because I'd forgotten where I put the SD card for safekeeping. After a frantic search, I finally noticed it in my keyboard tray, hidden beneath one of the batteries I'd put there...
Got the SD card reinstalled, batteries installed, battery cover installed, turned it on, set the clock...
...and noticed not much "different" from the way it was before sending on vacation. Well, the display isn't the cool blue from the original, but more of a very dim, slightly yellowish tint.
In the morning when my eyes are fresh and better focused, I'll check the firmware and resent my display preferences.