(legal wife appealed probate court decision requiring her to tender proceeds of life insurance policy back to estate; wife and decedent had consent judgment of separate maintenance, which specifically stated wife had no further interest as beneficiary of life insurance; insurer denied claim by estate for proceeds stating under ERISA it could only pay designated beneficiary under the policy which was the wife; probate court held wife had waived her rights to the proceeds; on appeal court affirmed probate court holding that under contract law, once proceeds properly paid pursuant to ERISA, a contract claim could be made against wife for the proceeds she waived in the maintenance agreement; remanded to probate court to examine issue raised by wife that she and decedent entered into new agreement).