Civil registration of Catholic marriages started in 1864, so no cert will be available - just the parish record.
Details from parish records are often provided as transcripts, as on the RootsIreland website. In some cases images from the registers are also available, as on some parishes on the IrishGenealogy website - this covers Co. Kerry and parts of Dublin, Cork & Carlow
The other way to access the records is to visit the National Library. Some of the film readers in the research room have a scanner and printer attached, where you print selected pages for reference.