From my experience it depends on the channel you buy through. For standard Ritchie Bros auctions it is mostly buyer responsibility after the sale, so inspections and due diligence matter a lot. That said their support teams are usually responsive with documents, logistics, and export help.
If you buy through IronPlanet or Marketplace E there tends to be a bit more structure around condition reports and post sale questions. For first time buyers I would recommend reading the inspection reports carefully, asking questions before bidding, and budgeting for transport and minor fixes right away.