Most local authority websites have pretty good FAQ pages on PP guidelines, making a PApp, etc. Have a look at Dublin City Council, Fingal County Council and others.
Re planning law-
Yvonne Scannell's 'Envoronmental and planning law in Ireland' has just been revised as 'Environmental and land use law'.
Then there's Eamonn Galligan's 'Irish planning law and procedure' from 1997, which obviously pre-dates the 2000 Act.
'The Irish planning law factbook' by Berna Grist and others is a loose leaf publication from 2003, therefore capable of being updated periodically. But it's very pricey.