I am the trustee for my late parent''s trust and executor of her will. I wish to resign as trustee and executor. There is a successor trustee.

The trust document will tell you how to resign. Usually, the trustee who wishes to resign is required to submit something in writing, and if there is a successor trustee named in the trust, to notify the successor trust.  If you have Letters of Trusteeship issued by the County Surrogate's Office, they might require those to be turned over so that new Letters can bee issued to the successor trustee.