If they do not have the patch wire in your area the soldering will work. Just strip the insulation for a few inches and solder the strands into one solid wire. A solid wire will not wick where the stranded wires will wick the oil. Then tape each wire separate to replace the insulation you removed.
I'm comfy enough with a soldering iron, so that's the procedure I followed - with the stripped portions offset to ensure there's no chance of a contact even if the tape failed.
I was fortunate that the ECU showed zero sign of any oil ingress, nor could I see oil on the stranded wire when I stripped it, even though there seemed to be some showing on the connector face. I finished up with Deoxit on the various connectors (ECU etc) that I could readily get at, and I'm happy enough for now.
Having cleaned the area around the solenoid I'll watch it to see whether the seal leak is a slow burner or something that demands replacement sooner rather than later.
Thanks for all the notes on this issue, very helpful.