Search for Great-Great-Grandparents

I'm not sure that I have the correct parish, I was looking for Convoy or Conwall, but those two parishs don't show on your list. My great-great-grandparents were married in either of those churches in Letterkenny on 4 Jan 1825. They were James Elliott and Ann Clark. They were married by Dr. Joseph Stopford, whom I believe is buried in Conwall Church cemetery. James and Ann had 3 children in County Donegal, Margaret Anne  baptised Feb 1829 at Raphoe Cathederal. Parents gave residence as Dromore, Parish of Taughboyne, Stranorlar. Stephen was born 1833, no records, Jane was born Church Hill 1835, although I cannot find any records. I would like to visit Ireland in September and would like to have James and Ann's marriage certificate and also their townland residence. I am willing to pay for this search and these documents. James and Ann and three children left Ireland and settled in Glasgow in 1836 where they had three sons, including my grandfather, Joseph Stopford Elliott, born Glasgow 1847.