Good morning. Hopefully I can help guide you through properly changing the vehicle title. First, what state was the death certificate issued and on the death certificate what state is listed as his permanent place of residence? If he was declared to be a resident of Florida when he passed then his original executed Will needs to be deposited with the Clerk of the Court in the County in which he died. You do not need to do this in person. You may mail the original Will to the clerk and they will send you a receipt. Make sure to keep a copy.
Next, did he have any assets other than the vehicle in his sole name, such has a bank account or real estate? If no, and the only asset is the vehicle, then you do not need an attorney and file the proper forms yourself. Contact the Clerk's office in the County in which he died and ask for the small estate form packet that allows you transfer a vehicle without officially opening a probate estate. Counties tend to have their own forms and usually you can print them from their website. After you submit the completed form to the clerk, it will be submitted to the judge, and an Order will be entered. You will need this Order, along with the original vehicle title to transfer ownership.
Once you have this Order you will need to contact the Florida Department of Motor Vehicles since you are in Indiana and I assume do not want to go in person to a Florida DMV office. You are allowed to transfer title via the mail, as long as you have the original vehicle title and the order from the court. The Florida DMV will mail you the new vehicle titled, issued in the name of the person named in your father's Will to receive his estate.
When you receive the new Florida vehicle title you can go to the Indiana DMV and have the vehicle registered there. I know it seems like a lot but in the end it really is just a few forms that need to be filled out.
Please let me know if there is any additional questions or clarification you may need. Thank you!