And what would an appropriate response be?

Thanks so much...

It means 'How are you?' and is the usual way to say that in Conamara and other parts of Connaught.

The reply depends on how you are feeling, of course, and here are a few possibilities:

Tá mé go maith, go raibh maith agat. I am well, thank you.
(TAW meh guh MAH, GUH ruh MAH uh-gut. or GUH ruh MAH udd.)

Táim go maith. I am well (just a minor variation)
(TOYM guh MAH)

Go breá.
(guh BRAW)
Fine.

Go hiontach.
(guh HEEN-tukh)
wonderful

Mairim beo.
(MAH-rim BYOA)
Hanging in there.

Agus tú féin?
(UGG-us too HAYNE?)
And yourself?