One needs to consult with a customs broker, and there
are many in
business on both sides of the border.
For old equipment, the broker's fee will exceed the import duties you
could expect to pay. I've had people send me stuff from Canada, and
later received outrageous bills from customs brokers, usually for around
five times what I paid for the merchandise. As far as I'm concerned,
I have no established business relationship with these customs brokers.
I did not expect the sender to use such a broker, and was not told that
it would be done. So I have never paid them.