From past experience administration folders are vastly different than a simple Will. If there's a Will you can certainly get a copy from PRONI but administration files vary in what they contain (and the amount of useful information) depending on the individual case. To give some examples-
1) administration for a male relative, widower, with 2 small children- mentioned brothers in America (how long there, etc.), sisters in Ireland, letters from one of the sisters (married name, address) asking to look after the children
2) administration for another male relatives mentioned (on the form) there was only a surviving brother in U.S. (my great-grandfather) and a niece in Ireland who put in the application (her address included). Great-grandfather relinquished his share to niece so there was affidavit with his address in Philadelphia and signature. Paperwork also included inventory of farm, contents of house, etc. Most important of all it confirmed that a sister who I've been searching for years now died before her brother.