(a) Every lifetime trust shall be in writing and shall be executed and acknowledged by the person establishing such trust and, unless such person is the sole trustee, by at least one trustee thereof, in the manner required by the laws of this state for the recording of a conveyance of real property or, in lieu thereof, executed in the presence of two witnesses who shall affix their signatures to the trust instrument.

(b) Any amendment or revocation authorized by the trust shall be in writing and executed by the person authorized to amend or revoke the trust, and except as otherwise provided in the governing instrument, shall be acknowledged or witnessed in the manner required by paragraph (a) of this section, and shall take effect as of the date of such execution. Written notice of such amendment or revocation shall be delivered to at least one other trustee within a reasonable time if the person executing such amendment or revocation is not the sole trustee, but failure to give such notice shall not affect the validity of the amendment or revocation or the date upon which same shall take effect. No trustee shall be liable for any act reasonably taken in reliance on an existing trust instrument prior to actual receipt of notice of amendment or revocation thereof.