Maybe backup your most important stuff but honestly, you should be fine. If you do mess up something, it's really easy to fix. I recently had a problem with my /boot partition not being big enough so I couldn't do updates, so I deleted my swap and boot, repartitoned, couldn't boot Ubuntu or Windows and with a simple "reinstallation" (I just went through the installer to recreate GRUB) it was fixed. Piece of cake.