I received the replacement parts - one button, the short cable that is part of / attached to the left handle and the left side long cable that comes out of the base. Actually those parts do not require any "welding" (soldering). But . . .
I opened the throttle handle and before removing those existing parts I verified the problem was not with them by hooking up the new cable and button outside the handle first and confirming that the problem maintained. I also used a circuit tester to verify the small internal circuit board was not the issue.
That left disassembling the base - and after removing the dozen or so long screws that are obvious from the bottom I was not able to open it up. At that point I decided to stop and not do any harm. My manual dexterity is not that great, and WinWing provided no instructions - just parts. I am going to continue to raise a stink, but I am not hopeful.
Buyer beware.