Searching famine immigrant Patrick Cawley from Sligo

My great-grandfather Patrick Cawley emigrated to the USA from Sligo (Port of Sligo) in June of Black 47 and lived in upstate New York for his entire life. My research of American sources shows no mention of siblings or other family from Ireland so I have always assumed he was a lucky surviror of that terrible time. He was a Roman Catholic. Statements of his birth year in various American census documents indicate he was born around 1822. His death certificate provided by his wife who was 18 years his junior and illiterate, according to census results, lists his parents as Michael Cawley and Mary Grayham. An inquiry I mailed to the Sligo Heritage Centre 30 years ago found no results. Since then, I have learned that Greghan is a popular name in Sligo and caused me to wonder if my great-grandmother had got his mothers name wrong. Spelling has been a challenge throughout my research as I came to realize that 19th century folks and officials oftenrendered information orally instead of in written format. I have found family under Cawley, Cauley and Colley!

I will be in Sligo next month to tour the area and with the proliferation of the Internet wondered if some resources have been made available to long-distance, or even visiting, researchers. Any suggestions would be greatly appreciated.