Benny,
I don’t know of any books or websites, but the Heritage Council has a grants scheme that might be suitable. I’m not sure if a building has to be a Protected Structure in order to qualify for a grant, though. It would certainly help if it was a PS- would you think of trying to get it listed if it’s not already?
Your local authority should also have a grants scheme for conservation, but again this would probably depend on the building being a Protected Structure.
Also, there was a thesis done in the Department of Planning and Environmental Policy in UCD in 2005 on the re-use of old mill buildings. It might be useful, and it would definitely have a bibliography that should give you leads.
Good luck.