Document Questions Please

[billabong1]

Hello and thanks in advance for your help,

A couple quick questions for FBR for my wife. We're going through her US father and his Irish-born father.
1) Do we need marriage certs for her father and grandfather? They do ask for them but I wouldn't think they were needed when going through male lineage so there's no name change, but if that's what they want, we'll get them.
2) Do we need our own marriage cert? Same story, my wife didn't take my last name but we'll supply if needed.
3)How do we go about getting an Irish birth cert for 1891? When we looked him up before, I'm not sure the place still exists.

Thanks Again

[billabong1]

Another question I forgot - the name of my wife's grandfather changed from McIniff to McNeff at some point. Will we need to address that?