If you change you mind about being a donor, simply discard the donor card, or cross out the organ donation on your license. You should also inform your family of your decision. Signing a donor card, or the back of your driver's license, is a way for you to express your wishes. Although a signed and witnesed donor card is a legal document, your family's understanding and consent are very important. A properly signed donor card is recognized anywhere in the country as an expression of your interest.
All anatomic donations are in fact an extraordinary gift, the gift of life.
No, although age and health of a potential donor may affect what organs and tissues can be used, this is not decided until the time of death. The quality of medical and nursing care will not change. When medical personnel in local hospitals have a death, they call a local 24 hour hotline. The coordinator assists the referring hospital and the donor family with the legal and medical aspects of donation. Brain death is death.