zcat - I'm glad you've got an itinerary worked out! That takes half the stress out. I'm no help with Galway, but I think it took us somewhere around four hours to get between Dingle and Ennis (close to Shannon and a good town to stay in before a morning flight). I'm sure the maps say it will take less time, but we got lost in Tralee (easy to do) and hit construction and detours just after we got off the Kilimer-Tarbert ferry.

http://www.aaireland.ie/routes_classic/ can give you a pretty good estimate of distances and times. I've both beaten and done worse than times shown there. Daily circumstances can vary,so you never know what you will encounter - construction, sheep in the road, farm gear in front of you with road conditions and traffic not allowing for passing, etc.

As for where to spend 4 nights, I'd go Galway. Lots to do and see in the Connemara region. Galway was nice, but I actually preferred Clifden as a place to stay, and it's close to Kylemore Abbey and Connemara National Park. And yes, definitely go more than once!