The cost of amending a trust can vary, depending on whether you want to amend or restate it, and on prevailing attorney fees in the area and state in which you live. You should probably plan on spending from $350 to $1,000, but it could be money well spent. Forms are available if you want to attempt the changes on your own, but that can be risky if you don't have a background in law. It's too easy to make mistakes that could have unintended consequences and keep your trust from performing in the way you intended.