De-ATT Nexus 6? topic

I got a nexus 6 from ATT since I couldnt afford it outright, surprisingly no bloatware was installed on it besides the splash screen and ringtones (yes I had sim card in during setup). I wanted to get rid of the ATT splash screen and ringtones and I know that can only be accomplished by rooting and deleting the partition they are in. Question is: if I remove them now will the just be reinstalled when OTA update comes(I know I'll lose root)? Also will rooting and removing the partition void the warranty on a nexus device?