Dumb plumbing questions about Price-Pfister Trip Lever Waste and Overflow
assembly.

I have a 25 year old cast iron tub. I have noticed rust under the tub at the
drain, corrosion on the brass waste assembly, and a leak. I am trying to
repair it.

The waste elbow is located under the cast iron tub. A waste plug assembly is
located in the tub (the trim you see at the top of the drain). There is a
washer between them.

1) Should the washer go under the tub? This is where it is now, but the leak
worries me. A Danco part seems to show it above the tub, but this doesn't
seem right either.

2) Should I put plumber's putty or something between the waste plug assembly
and the tub?

3) Anything special to watch out for in this type of repair or other stuff I
should do as long as I am in there?

Thanks,

Joe M