Hi,
Your father will pay the solicitor for drawing up the will - some amount less than €100.
There is no obligation to use the same solicitor when executing the will and the normal approach would be to agree a fee with the solicitor before they do any work on the estate. It should not be a percentage fee but simply a set fee for the work involved (even if there's a house sale involved, there's no need for a percentage fee). If you're going to ask another solicitor to handle the estate, they'd probably need to see the will before they'd quote.
Its perfectly normal to discuss fees with a solicitor before they do any work so don't be afraid to ask.
Edit: the solicitor takes their agreed fees just before the final distribution of the estate. They should send the executors a written explanation of the charges and distribution before they distribute the proceeds.