I've built a site for a customer in Magento (version 1.4), and now need to copy the theme across to a new site for the same customer. Is transferring the theme as simple as copying the relevant folders from 'app' and 'skin' (and then activating in the new Magento installation)?

There are also several extensions I need to install - should I install them before moving the theme so they don't overwrite anything, or will the theme be unaffected by extensions?