For the insurance benefits, the insurance company should be contacted to change the beneficiary. A death annuity beneficiary designated through an insurance company cannot be altered by a separate contractual document.
The gift of the personal property can be revoked if it was gratuitous. Exactly how this is done may differ depending on the terms of the gift. If the gift was to vest when your friend dies, he should probably create a new, legally enforceable document revoking the past gift and specifying the new gift recipient. Your friend may want the assistance of an attorney if this is the case.
If this was just a contract gratuitously gifting personal property at some time in the future, your friend probably just needs to sign a new letter or document stating his intention to revoke the contract. However, to know for sure whether this is possible, the terms of the contract would need to be reviewed.