Can I work on a new theme while leaving the current site up and running?

Hi,

I have a website up and running but I want to change the theme so I can redesign my website so I can have more flexibility with certain features.

Is there anyway I can work on the new theme and design while leaving the old one running until I am ready to launch the new design? I have installed a number of themes and run live preview, but I get the feeling if I were to save the new theme my current site would be overwritten and I’d need to redesign everything again – is this correct?

Also if I launched the new theme and did not like it, could I easily restore my old theme and all its settings?

I have also created a new site design and layout in iWeb – is there anyway this can be transferred easily across to WordPress?

Thanks in advance,