Do I need to replace the washer after I flush the ATF? If so where can I get one?

 

I would, on the last drain. Dealer or where ever you get the oil drain plugs from. I'm pretty sure they are aluminum.

 

They are an aluminium crush washer, you can get them on ebay for a dollar or so, I didn't change mine last time because I misplaced the one I had bought, but I will next time, because about 10 minutes after I had put the last oil change in, I found it in the ash tray of the car :\

 

They are available at auto parts stores too.

 

As I also need an antenna mast I ordered that and washers from FCP.