They're service parts. This is no different than any other service part for anything else. You buy the part you need, and its assumed you know what you're doing to replace it (otherwise you would have taken it to the repair man).
Brake calipers dont come with brackets, pads, slide pins, bolts and springs, Those are sold separately if you need them. Replacement freezer doors don't come with the ice maker panel in them, you transfer it over with the water line and the power connections. And so on.
No different here. Because a model train service tech knows how to solder.
This would be a good time to learn how, it'll only take a few minutes and I suspect the cost of taking James to a service center and paying to have the motor soldered in would get close to buying another James.
