You should not be trying to handle a Probate action without being represented by an Attorney. First of all if it really is a very small estate, you may not have had to even Probate it, which the Attorney would have advised you. Also, understand that as an executor you are a fiduciary, owing a very high duty to the estate and the heirs. That means you could be personally liable for any errors you make in complying with the provisions of the probate act, even if the errors were innocent. As pointed out to you, the Court will probably convert the matter to a supervised estate, which will require you to get the Court's permission before taking many actions. This means you will be spending a lot more time on the matter. I suggest that you hire a Probate Attorney immediately, and see if he or she can reach an accomodation with the 3 siblings. This would save both time and money.
Disclaimer. The information contained in this answer is provided for informational purposes only, and should not be construed as specific legal advice, further is not intended and it does not constitute or create an attorney-client relationship between The Law Office of James C. Siebert & Associates and any recipients. No recipient of this answer should act or refrain from acting on the basis of this answer without seeking the appropriate legal advice on the particular facts and circumstances at issue from an attorney licensed in the recipient's state. Under Illinois ethical rules answers to questions might be considered as advertisement and therefore please consider the answer to the question is ADVERTISING MATERIAL.
If there is a question about your actions as executor, you will probably be ordered to furnish accountings. Get a good probate lawyer and stop trying to do this yourself.
Your story does sound interesting. A court is unlikely to order monthly accountings but they will likely order an accounting now. Additionally the court will likely convert the estate to supervised.
Lastly, the judge will likely highly recommend that you hire an attorney to handle the estate.
Legal Disclaimer: Paul A. Smolinski is licensed to practice law in the State of Illinois only, and as such, his answers to AVVO inquiries are based on his understanding of Illinois law only. His answers are for general information about perceived legal issues within this question only and no response to any posted inquiry should be deemed to extend any right of confidentiality between you and Mr. Smolinski, to constitute legal advice, or create an attorney/client or other contractual relationship. An attorney/client relationship is formed only by specific agreement including an evaluation of the specific legal problem and review of all the facts and documents at issue. We try to insure the accuracy of this information, but we cannot guarantee its accuracy. The reader should never assume that this information applies to his or her specific situation or constitutes legal advice. Therefore, please consult competent counsel that practices in the subject area in your jurisdiction and who is familiar with your specific facts and all of the circumstances.