Gorman/O'Brien Marriage 1852

In 1978 on a visit to Ireland from Canada, my mother obtained an "extract from the marriage register" of the Parish of Mitchelstown, Diocese of Cloyne (sp.?) signed by Rev. John Sheehan and dated 15 Sept.1978.  It referred to the marriage on 15 August 1852 of my great-great grandparents, Gerald (?) Gorman and Johanna O'Brien.  He was known here in Canada as Gerald but the name on the extract is handwritten and actually looks more like "Garrett" or "Garrelt" Gorman.  I have been trying to find out more about these ancestors before my daughter visits Ireland this summer - but I haven't been having any luck.  I thought it would be advisable to get clarification of my 2X grandfather's name in this regard and wondered if anyone could check this out for me in the parish records.  Family history has it that both Gerald (?) and Johanna were from Limerick.  I don't know if that meant the county or the city.  Any advice or assistance would be greatly appreciated.  regards, Pam Devine