What many Poles do is this: they would declare the tractor is used (not new) and its value is... $35. Then you don't have to pay any tax at all. It worked for me many times when I was sending a computer or... a small lawn mower to Poland. This is a heavy stuff so I'm not sure it woud work though, but you can try :).
Go to Polamer or Doma shipping office and they would put their own cartons on your original package, put it on a ship and it's free to go. I don't think they check it (used stuff can have new packaging too after all). I'm not sure about tax as I never had to pay that.. If anything, you can call them to find out about the tax - they should tell you over the phone - polamercargo.com/_webpc/kontakt.aspx
