I am sorry to learn of this situation.
Unfortunately there isn't going to be a form for this, you are going to have to draft a motion (it is going to be a motion for "Breach of Fiduciary Duty" and "Removal of Personal Representative of the Estate")
You can usually find good templates for these motions at your local law library (look specifically for a set of books called "practice guides" these are books used by attorneys with strategy tips, references to commonly used legal authorities, and templates for common motions, pleadings, etc.). Your local law librarian will be able to point you to the most effective books for your specific circumstance in their library.
It appears that the court is already aware of the circumstances as they have not bought into your sister's "relabelling" so you are headed in a positive direction. I always recommend retaining a lawyer if at all possible (a lawyer does not give you any additional legal rights, but they can help you more fully exercise all of your rights), but if you do plan on going this on your own, you will want to visit your local law library (attorneys spend a great deal of time researching cases and using templates when drafting their motions, if you are representing yourself, you need to do the same.
I am sorry to learn of your loss, and I do wish you the very best with this matter.