Hi Konrad, bad news, the entire unit needs to be removed and disassembled, all the ones I find close to yours have keyways and snap rings,the front plate is for changing seal only,, the shaft has to come out the back.
I wish I had better news.
I will still look at a couple other places for a complete manual but I figured at least you can start pulling apart, I would take pictures along the way with phone so there is no question about reassembly,,also mark all gear to gears in case gears need to be timed during assembly,as long as it goes back the same way it will stay in time.
The other expert agrees it must be torn apart.
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