If you are planning to redesign your Wild Apricot site live on Wild Apricot, you should contact Wild Apricot about setting up a clone site.
The clone site is a limited copy of your existing site with a different URL. It won’t have all the member records, and there’s a limit of file space that will be carried over, so you may not find all the PDFs or images that your existing site contains when the clone is created by Wild Apricot support. But that doesn’t matter – the clone is only for your work in doing the redesign prep: theme, template changes, CSS alterations, layouts, etc. You don’t want to do this work on the live site until you have everything absolutely determined.
But… Wild Apricot is only going to provide you an operational version of the clone site for about 30 days, so no need to ask for it until you have “the look” approved. And this is just about working out the details for the redesign – all you do will have to be implemented again on your actual existing site once you are ready, The clone site is just for preparatory purposes.