The microphones usually have visible coverings in the headliner. However if privacy is your concern, just disabling the celluar modem should be enough.

As for voiding any warranty, should a problem arrise, it's up to the manufacturer to prove that whatever you did caused damage. Just taking apart and reassembling a console correctly will not void your warranty. "Warranty Voided if removed/opened" labels are not legally-enforceable in the US.

Just look for Youtube videos on how to take it apart (or look for repair videos for other items in the console).