Use Irish Family History Federation's rootsireland.ie website to search for and pay for the information you want. You can get a certain amount free. For example, there's a birth or baptism of an Anne Colgan in Co Meath (where Summerhill - one word!) is located in 1824. For about 4 or five euro you can get the entry. Bear in mind that the quality of some of these entries is not good; they were put together in a 'workfare'/training scheme for young unemployed persons, who may not be familiar with local names... However, if you are not happy with the results, you can check a microfilmed copy of the parish register in the National Library of Ireland on Kildare St, Dublin, for free, and read the entry yourself.

I have found no marriage of McGowan to Colgan in my records (over 3,000 Colgan marriages and over 9,000 Colgan-participant births or baptisms.)