This is where the advice of a solicitor is invaluable. While he may be well able to take out probate he will still need a solicitor for sale of the property and for the sake of a few thousand euro he might be able to prevent siblings falling out over a parents will.
Answering simple questions such as can we transfer this apartment to my sister at €250K value and that be a portion of her third would be answered instantly by a solicitor who would advise the executor.