The money transaction stuff is straight forward. US cash is readily exchangeable at any charter bank in Canada. You may want to contact the US branch of RBC Royal Bank and ask about opening an account with them you can access from within Canada so you don't need to transport cash across the border etc. You can also email the funds to the seller right at their kitchen table if your bank supports that service.
It's the import export stuff you want to get right. Call the US Customs house at your proposed re-entry point to the US and ask what documentation you need. Then check with your state and county to make sure they don't have some goofy required inspection ($$ grab)...
