第一个问题，google "how to unregister my car in XX state".
As long as you file the paperwork to remove the car under your name, you won't be held liable. Do this before the stranger take the car. In some states you need to remove the license plate, in some states the license plates goes with the car. Ask your DMV.
第二个问题，google "how to donate my car in XX city". Try salvation army, good will. You may deduct the donation from your taxes, if you do itemized deduction.
