You only need to do the following steps and all your data will be in the new version of Magento:
1) Make a database backup of your current live site.
2) Get the newest version of Magento in a test enviroment
3) Restore you database to your test enviroment and point your new version to this new database.
4) Run your site, it will upgrade your database and all your customer data will be there!
It is like Magic but with less work.
After that you can install you modules and your theme.
... View more