For future reference: I found a video illustrating the process https://www.youtube.com/watch?v=IdLdFgso... I needed to use a fair amount of force to get the sides off but it was possible. On of the little tabs got torn in the process but there was no problem getting it securely back together. One could be a little concerned about the degree of water-proofness. I was possible to replace the batteries with new AA NiMH. In my case, I did not have to solder them in.
Thanks a lot. I can only agree with the comment on magnetic screwdrivers.
Also, notice that there are two types of screws: flat head and countersunk head. They also differ slightly in length.
I had a lot of trouble with wires getting stuck but a few tries and some care help.
Further, when assembling the push button and the rotating mechanisms I needed to pay attention to two tiny taps that fit into one of the two clamshells.
Finally, the tiny switch sensing the diffusing disc panel needed to be seated in two holes. I managed to assemble the flash only to discover that the sensing didn't work.