Thanks for the reply Gwinter!
Meanwhile, the fabricated bleeder-look-a-like is in and I got a call from my mechanic yesterday to go there with my laptop and do the calibration routines.
I got there and we first bled the system, which took us most of the time, because the pressure would build up and then come back down, over and over again... At last, we managed to get the pressure up at around 50ish bar and steady!
I did the bleed routine, with the brake pedal pressed, (a couple of times...) and I got it to succeed!
I then did the Service/EOL routine (had to do it two or three times, because it was not working right) and got it to succeed at last!
Started the car, and shifted the gears (1, 2, N, R) without any problems.
Switched off the car and with the key in MAR, did the entire sequence: 1, 2, 3, 4, 5, 4, 3, 2, 1, N, R, N. All good!
The car is getting prepped to go back home today, if all goes well!
I'll let you know how it drives with the new gearbox and all.
Thanks for all your inputs guys!
I'll post some picks of the old gearbox later on...