Hello and thanks for your question. My name is XXXXX XXXXX I will do all I can to help.
If you get a used switch, Then you may get SOME functionality out of it.
To answer your first question, the answer is YES, A new switch does require a software download to make the new switch functional. as it is on the low speed CAN network.
I have put a used switch in an XC90 before, (not recommended) and everything worked, BUT, the power mirrors.
So in summary, A new switch does require software download to be functional.
A used switch may work , but sometimes they have limited functionality.
A new switch will not work without programming.
Let me know if you have any further questions. Thank you.
ok great info, thanks! im going to try to clean it up/resolder it tomorrow, but if that doesn't work ill just bite the bullet and have it programmed once replaced. its still half the price of a lexus power window switch :) (was $800 on my rx300)