Liability for a home repair company

So fixers, I have recently been seriously considering using this incredible website to begin to fix things in my community, of course using one of your kits. My biggest question is, however, how have you handled liability for repairs? For example, say I am repairing the dock connector in and iPhone 6 plus. This obviously involves the removal of some very delicate machinery, and I am wondering, who is liable if something goes wrong. Do I have the customer sign a waiver before I begin work? Or do I simply go into the repair with and understanding of you break it you buy it? Thanks for any help.