I am trustee of family trus, I want to do short sale. They are asking me for a court stamped letter of testamentary. How do I get one?

If they are asking for letters testamentary then the house is probably not properly "in" the trust. You might be better off to just walk away!? I would talk to an attorney about your whole case to decide what's best. If you do decide to go through with getting letters testamentary you would file in the probate court of the county where they lived. You might qualify for a Heggstad petition also so look into that as an option. Good luck.  -John