Most attorneys handle estate work on an hourly rate. Some will handle probating an estate for a flat fee. Be sure to ask the attorneys for estimate in either case.
There are a lot of factors to consider, all of which will affect legal fees. Call around and get some quotes. Some attorneys may charge a flat fee to handle a will while others may charge hourly. The more involved the matter, the longer it will take.
Attorney fees vary depending on the jurisdiction. The fees are usually dependent on the value of the estate. An average fee is usually 3% of the value of the estate. A lower valued estate may have to pay more then 3% and a high value estate may pay less.
Each attorney is different. Some charge by the hour and some charge a flat rate. It depends on the amount of your fathers estate and how much work it requires.