John,
Tom gave you some excellent suggestions for parts. As to traction tires, they rarely wear out for some reason. They're vulcanized to the metal and unless they've been severely mistreated, they'll last for a long time. Not to say that they don't sometimes chip, however.
As to your door, I have an orphan one I can send to you gratis. Do you also need the latch and pin? How about the door tracks? They're out there. I can also send you the pin and latch if needed.
Along with Tom, I sometimes find the parts I need at larger train shows. Depending on where yo live, the upcoming Spring S Spree is a good place to find most anything you will need for classic Flyer.
I would also add to Tom's list replacement couplers, both link (along with the pin) and knuckle ones if you have not already bought some.
