The users would need to be imported separately, and for that you may want to try a
plugin before you even purchase/install the theme just to make sure this works well on a standard WordPress installation. There also appears to be
other solutions which can be found in a Google search if you don't have success with the plugin. After that is done, you can use the built in
.csv importer in ClassiPress to import the actual data (which of course means you need to get your current listings in .csv format though. Thanks.