After posting I opened my eyes and realized the obvious: there's a metal frame at the top front of the washing machine (behind the control panel) which can be removed with 4 screws! This allowed me to attach the water valve first, then have enough room to (firmly but carefully) push the water distributor forward and attach it to the water valve. Pictures say more than words, so see below.
As you can see, I also disconnected the cable from the front control panel (buttons, display etc.) which wasn't easy and could possibly risk damaging the cable/plug. In hindsight I could probably just leave the front panel dangling and still be able to attach the water valve/water distributor.
You can see how it's now possible to attach the new parts, with the extra room in the front. Note that the front end of the water distributor is to be aligned with the holes in the metal frame (after the metal frame and front panel has been re-attached), with screws on the right hand side (view from front).
When attaching the existing cable connectors to the water distributor I found they didn't fit! The two connectors were all wrong -the old water distributor didn't have any such connectors, but the mating connectors went directly on a couple of electronic circuit board (PCB) "slots". It turned out the white plastic "frames" on the new water distributor were easily removable by pulling them outwards with pliers! Then the old connectors would fit. See photo below:
I suppose the water distributor might be used with other washing machine models using different connectors or later sales of this washing machine had revised cable designs or something.
The good news is that now, with a new water distributor, water valve, door-switch and a good cleaning (I took the time to manually clean the inside of the water inlet dispenser-hose (filled with grime), the inside of the rubber door-seal (also filled with dirt) as well as the water outlet (front left bottom of the machine) to get rid of any sand and dirt. Finally I've given it a full 95 degree cycle with one of those cleaning packs from the local supermarket. I won't be surprised if our clothes get a lot cleaner after all this!
By the way, can someone suggest what I do about all the rust spots below where the detergent drawer goes (1st photo in this posting)? I believe there are enamel repair kits, but based on prior experience they haven't really worked that well.