I don't want to make it a hobby and I agree its just a washer. I wonder if there is some planned obsolescence going on here. Circuit boards should last longer than they do in appliances. As far as the PLC, I have done similar things in the past and I get tremendous satisfaction when I fix an annoying problem, and the problem is fixed for the LONG term.
There was a relay on my furnace some years back in a different home. This relay had a circuit board in it that gave a time delay when shutting off the heat pump compressor. Great idea, but if the circuit board failed, the fan would run 24-7. After two failures and several hundred dollars in repairs, I bought a repeat cycle timer and a couple of relays and wired it my own way. No more failures after that.
With electronics as common as they are today, the washer people should be able to design a circuit board that will last for years and when it does have a rare failure, it should cost about $30, not $300.