You need to install Kies in order to backup the data from your phone. By default, when you connect the phone to PC, the USB Mass Storage should be enabled automatically. You can copy the entire folders and content from internal and external storage (if you have any!) then you can restore it when it's fixed.
Install Kies, then connect the phone and wait for the program to detect it. Create a backup, send it to repairs and then you can restore it the same way you created the backup.