You may consider driving down to Croatia with a van of furniture to stock your house once you have bought a property. This may well lead to problems at the Slovenian border.
The Customs officials are there to make sure that goods are not smuggled into Croatia without paying VAT and Duty. The Croatian government wants to protect their local industry from imported goods.
If it is second hand/used goods there would be no import duty. Just be firm that all you are importing is "used goods" (upotrebljene stvari) and nothing new (nista novo).
It is worthwhile creating yourself a manifest of all items so that when they want to check you have something to show them and it saves turning everything out. Make sure that you get through to the official that not only is it second hand, but that it is for your own personal use and will not be sold or used for any commercial purpose.
The official customs website (English version planned!) is at: www.carina.hr.
For guaranteed delivery use reputable a transport company that has experience of moving goods between Croatia and your home country.
Ensure you receive a written quote that covers ALL COSTS involved (plus a specified amount of duty, etc) and that the goods will be delivered to the end destination by a certain date.
It's also very important to get the right import code on the paperwork and not leave it to customs to decide which tariff to apply. A 'Tariff' is produced by product code with rates of duty varying between codes and sometimes within code sub groups.
It gets even more complicated if foodstuffs are involved as EU agricultural levies start to come into play and they can be positive or negative! On top of any liability for Duty you will also have a liability for VAT (pdv), which is based on the value of the goods.