There is a procedure for trying to remove a fiduciary, but the important questions you will have to answer to the judge, are why you want to swap out the current fiduciary, has he/she done anything wrong, are they conducting themselves appropriately, and whether you might have an axe to grind in wanting the current fiduciary replaced.
In my experience, the Probate Judges I have met and appeared in front of, are for the most part, “street smart” individuals, trained in the law, who want to do the right thing. They will see through a “Petition to Modify Estate” (the formal device used to replace a fiduciary) that is filed for less than appropriate reasons. If you are looking to replace the current fiduciary yourself, the question you will have to answer as well, is whether you have priority as appointment as a fiduciary.
The actual procedure will depend on whether you are concerned with a Decedent's Estate, a Guardianship, or a Conservatorship. Just click on the appropriate term, and you will be taken to the appropriate Petition form, to change the fiduciary.